Update re2

third_party/re2/doc/syntax.txt

 RE2 regular expression syntax reference
 -------------------------­-------­-----
 
 Single characters:
 .       any character, possibly including newline (s=true)
 [xyz]   character class
 [^xyz]  negated character class
 \d      Perl character class
 \D      negated Perl character class
-[:alpha:]       ASCII character class
-[:^alpha:]      negated ASCII character class
+[[:alpha:]]     ASCII character class
+[[:^alpha:]]    negated ASCII character class
 \pN     Unicode character class (one-letter name)
 \p{Greek}       Unicode character class
 \PN     negated Unicode character class (one-letter name)
 \P{Greek}       negated Unicode character class
 
 Composites:
 xy      «x» followed by «y»
 x|y     «x» or «y» (prefer «x»)
 
 Repetitions:
 x*      zero or more «x», prefer more
 x+      one or more «x», prefer more
 x?      zero or one «x», prefer one
 x{n,m}  «n» or «n»+1 or ... or «m» «x», prefer more
 x{n,}   «n» or more «x», prefer more
 x{n}    exactly «n» «x»
 x*?     zero or more «x», prefer fewer
 x+?     one or more «x», prefer fewer
 x??     zero or one «x», prefer zero
 x{n,m}? «n» or «n»+1 or ... or «m» «x», prefer fewer
 x{n,}?  «n» or more «x», prefer fewer
 x{n}?   exactly «n» «x»
 x{}     (== x*) NOT SUPPORTED vim
 x{-}    (== x*?) NOT SUPPORTED vim
 x{-n}   (== x{n}?) NOT SUPPORTED vim
 x=      (== x?) NOT SUPPORTED vim
 
+Implementation restriction: The counting forms «x{n,m}», «x{n,}», and «x{n}»
+reject forms that create a minimum or maximum repetition count above 1000.
+Unlimited repetitions are not subject to this restriction.
+
 Possessive repetitions:
 x*+     zero or more «x», possessive NOT SUPPORTED
 x++     one or more «x», possessive NOT SUPPORTED
 x?+     zero or one «x», possessive NOT SUPPORTED
 x{n,m}+ «n» or ... or «m» «x», possessive NOT SUPPORTED
 x{n,}+  «n» or more «x», possessive NOT SUPPORTED
 x{n}+   exactly «n» «x», possessive NOT SUPPORTED
 
 Grouping:
-(re)    numbered capturing group
-(?P<name>re)    named & numbered capturing group
-(?<name>re)     named & numbered capturing group NOT SUPPORTED
-(?'name're)     named & numbered capturing group NOT SUPPORTED
+(re)    numbered capturing group (submatch)
+(?P<name>re)    named & numbered capturing group (submatch)
+(?<name>re)     named & numbered capturing group (submatch) NOT SUPPORTED
+(?'name're)     named & numbered capturing group (submatch) NOT SUPPORTED
 (?:re)  non-capturing group
 (?flags)        set flags within current group; non-capturing
 (?flags:re)     set flags during re; non-capturing
 (?#text)        comment NOT SUPPORTED
 (?|x|y|z)       branch numbering reset NOT SUPPORTED
 (?>re)  possessive match of «re» NOT SUPPORTED
 re@>    possessive match of «re» NOT SUPPORTED vim
 %(re)   non-capturing group NOT SUPPORTED vim
 
 Flags:
 i       case-insensitive (default false)
 m       multi-line mode: «^» and «$» match begin/end line in addition to begin/end text (default false)
 s       let «.» match «\n» (default false)
 U       ungreedy: swap meaning of «x*» and «x*?», «x+» and «x+?», etc (default false)
 Flag syntax is «xyz» (set) or «-xyz» (clear) or «xy-z» (set «xy», clear «z»).
 
 Empty strings:
 ^       at beginning of text or line («m»=true)
 $       at end of text (like «\z» not «\Z») or line («m»=true)
 \A      at beginning of text
-\b      at word boundary («\w» on one side and «\W», «\A», or «\z» on the other)
-\B      not a word boundary
+\b      at ASCII word boundary («\w» on one side and «\W», «\A», or «\z» on the other)
+\B      not at ASCII word boundary
 \G      at beginning of subtext being searched NOT SUPPORTED pcre
 \G      at end of last match NOT SUPPORTED perl
 \Z      at end of text, or before newline at end of text NOT SUPPORTED
 \z      at end of text
 (?=re)  before text matching «re» NOT SUPPORTED
 (?!re)  before text not matching «re» NOT SUPPORTED
 (?<=re) after text matching «re» NOT SUPPORTED
 (?<!re) after text not matching «re» NOT SUPPORTED
 re&     before text matching «re» NOT SUPPORTED vim
 re@=    before text matching «re» NOT SUPPORTED vim
@@ skipping 64 matching lines @@
 Named character classes as character class elements:
 [\d]    digits (== \d)
 [^\d]   not digits (== \D)
 [\D]    not digits (== \D)
 [^\D]   not not digits (== \d)
 [[:name:]]      named ASCII class inside character class (== [:name:])
 [^[:name:]]     named ASCII class inside negated character class (== [:^name:])
 [\p{Name}]      named Unicode property inside character class (== \p{Name})
 [^\p{Name}]     named Unicode property inside negated character class (== \P{Name})
 
-Perl character classes:
+Perl character classes (all ASCII-only):
 \d      digits (== [0-9])
 \D      not digits (== [^0-9])
 \s      whitespace (== [\t\n\f\r ])
 \S      not whitespace (== [^\t\n\f\r ])
 \w      word characters (== [0-9A-Za-z_])
 \W      not word characters (== [^0-9A-Za-z_])
 
 \h      horizontal space NOT SUPPORTED
 \H      not horizontal space NOT SUPPORTED
 \v      vertical space NOT SUPPORTED
 \V      not vertical space NOT SUPPORTED
 
 ASCII character classes:
-[:alnum:]       alphanumeric (== [0-9A-Za-z])
-[:alpha:]       alphabetic (== [A-Za-z])
-[:ascii:]       ASCII (== [\x00-\x7F])
-[:blank:]       blank (== [\t ])
-[:cntrl:]       control (== [\x00-\x1F\x7F])
-[:digit:]       digits (== [0-9])
-[:graph:]       graphical (== [!-~] == [A-Za-z0-9!"#$%&'()*+,\-./:;<=>?@[\\\]^_`{|}~])
-[:lower:]       lower case (== [a-z])
-[:print:]       printable (== [ -~] == [ [:graph:]])
-[:punct:]       punctuation (== [!-/:-@[-`{-~])
-[:space:]       whitespace (== [\t\n\v\f\r ])
-[:upper:]       upper case (== [A-Z])
-[:word:]        word characters (== [0-9A-Za-z_])
-[:xdigit:]      hex digit (== [0-9A-Fa-f])
+[[:alnum:]]     alphanumeric (== [0-9A-Za-z])
+[[:alpha:]]     alphabetic (== [A-Za-z])
+[[:ascii:]]     ASCII (== [\x00-\x7F])
+[[:blank:]]     blank (== [\t ])
+[[:cntrl:]]     control (== [\x00-\x1F\x7F])
+[[:digit:]]     digits (== [0-9])
+[[:graph:]]     graphical (== [!-~] == [A-Za-z0-9!"#$%&'()*+,\-./:;<=>?@[\\\]^_`{|}~])
+[[:lower:]]     lower case (== [a-z])
+[[:print:]]     printable (== [ -~] == [ [:graph:]])
+[[:punct:]]     punctuation (== [!-/:-@[-`{-~])
+[[:space:]]     whitespace (== [\t\n\v\f\r ])
+[[:upper:]]     upper case (== [A-Z])
+[[:word:]]      word characters (== [0-9A-Za-z_])
+[[:xdigit:]]    hex digit (== [0-9A-Fa-f])
 
 Unicode character class names--general category:
 C       other
 Cc      control
 Cf      format
 Cn      unassigned code points NOT SUPPORTED
 Co      private use
 Cs      surrogate
 L       letter
 LC      cased letter NOT SUPPORTED
@@ skipping 26 matching lines @@
 So      other symbol
 Z       separator
 Zl      line separator
 Zp      paragraph separator
 Zs      space separator
 
 Unicode character class names--scripts:
 Arabic  Arabic
 Armenian        Armenian
 Balinese        Balinese
+Bamum   Bamum
+Batak   Batak
 Bengali Bengali
 Bopomofo        Bopomofo
+Brahmi  Brahmi
 Braille Braille
 Buginese        Buginese
 Buhid   Buhid
 Canadian_Aboriginal     Canadian Aboriginal
 Carian  Carian
+Chakma  Chakma
 Cham    Cham
 Cherokee        Cherokee
 Common  characters not specific to one script
 Coptic  Coptic
 Cuneiform       Cuneiform
 Cypriot Cypriot
 Cyrillic        Cyrillic
 Deseret Deseret
 Devanagari      Devanagari
+Egyptian_Hieroglyphs    Egyptian Hieroglyphs
 Ethiopic        Ethiopic
 Georgian        Georgian
 Glagolitic      Glagolitic
 Gothic  Gothic
 Greek   Greek
 Gujarati        Gujarati
 Gurmukhi        Gurmukhi
 Han     Han
 Hangul  Hangul
 Hanunoo Hanunoo
 Hebrew  Hebrew
 Hiragana        Hiragana
+Imperial_Aramaic        Imperial Aramaic
 Inherited       inherit script from previous character
+Inscriptional_Pahlavi   Inscriptional Pahlavi
+Inscriptional_Parthian  Inscriptional Parthian
+Javanese        Javanese
+Kaithi  Kaithi
 Kannada Kannada
 Katakana        Katakana
 Kayah_Li        Kayah Li
 Kharoshthi      Kharoshthi
 Khmer   Khmer
 Lao     Lao
 Latin   Latin
 Lepcha  Lepcha
 Limbu   Limbu
 Linear_B        Linear B
 Lycian  Lycian
 Lydian  Lydian
 Malayalam       Malayalam
+Mandaic Mandaic
+Meetei_Mayek    Meetei Mayek
+Meroitic_Cursive        Meroitic Cursive
+Meroitic_Hieroglyphs    Meroitic Hieroglyphs
+Miao    Miao
 Mongolian       Mongolian
 Myanmar Myanmar
 New_Tai_Lue     New Tai Lue (aka Simplified Tai Lue)
 Nko     Nko
 Ogham   Ogham
 Ol_Chiki        Ol Chiki
 Old_Italic      Old Italic
 Old_Persian     Old Persian
+Old_South_Arabian       Old South Arabian
+Old_Turkic      Old Turkic
 Oriya   Oriya
 Osmanya Osmanya
 Phags_Pa        'Phags Pa
 Phoenician      Phoenician
 Rejang  Rejang
 Runic   Runic
 Saurashtra      Saurashtra
+Sharada Sharada
 Shavian Shavian
 Sinhala Sinhala
+Sora_Sompeng    Sora Sompeng
 Sundanese       Sundanese
 Syloti_Nagri    Syloti Nagri
 Syriac  Syriac
 Tagalog Tagalog
 Tagbanwa        Tagbanwa
 Tai_Le  Tai Le
+Tai_Tham        Tai Tham
+Tai_Viet        Tai Viet
+Takri   Takri
 Tamil   Tamil
 Telugu  Telugu
 Thaana  Thaana
 Thai    Thai
 Tibetan Tibetan
 Tifinagh        Tifinagh
 Ugaritic        Ugaritic
 Vai     Vai
 Yi      Yi
 
@@ skipping 57 matching lines @@
 (*SKIP) NOT SUPPORTED
 (*THEN) NOT SUPPORTED
 (*ANY)  set newline convention NOT SUPPORTED
 (*ANYCRLF)      NOT SUPPORTED
 (*CR)   NOT SUPPORTED
 (*CRLF) NOT SUPPORTED
 (*LF)   NOT SUPPORTED
 (*BSR_ANYCRLF)  set \R convention NOT SUPPORTED pcre
 (*BSR_UNICODE)  NOT SUPPORTED pcre