Apply ICU patches for ICU tickets 6175 (ISO-2022 and ...

third_party/icu38/public/common/unicode/ucnv.h

Index: third_party/icu38/public/common/unicode/ucnv.h
===================================================================
--- third_party/icu38/public/common/unicode/ucnv.h	(revision 10949)
+++ third_party/icu38/public/common/unicode/ucnv.h	(working copy)
@@ -870,6 +870,8 @@
 typedef enum UConverterUnicodeSet {
     /** Select the set of roundtrippable Unicode code points. @stable ICU 2.6 */
     UCNV_ROUNDTRIP_SET,
+    /** Select the set of Unicode code points with roundtrip or fallback mappings. @draft ICU 4.0 */
+    UCNV_ROUNDTRIP_AND_FALLBACK_SET,
     /** Number of UConverterUnicodeSet selectors. @stable ICU 2.6 */
     UCNV_SET_COUNT
 } UConverterUnicodeSet;
@@ -878,11 +880,16 @@
 /**
  * Returns the set of Unicode code points that can be converted by an ICU converter.
  *
- * The current implementation returns only one kind of set (UCNV_ROUNDTRIP_SET):
+ * Returns one of several kinds of set:
+ *
+ * 1. UCNV_ROUNDTRIP_SET
+ *
  * The set of all Unicode code points that can be roundtrip-converted
- * (converted without any data loss) with the converter.
+ * (converted without any data loss) with the converter (ucnv_fromUnicode()).
  * This set will not include code points that have fallback mappings
  * or are only the result of reverse fallback mappings.
+ * This set will also not include PUA code points with fallbacks, although
+ * ucnv_fromUnicode() will always uses those mappings despite ucnv_setFallback().
  * See UTR #22 "Character Mapping Markup Language"
  * at http://www.unicode.org/reports/tr22/
  *
@@ -893,6 +900,12 @@
  *   by comparing its roundtrip set with the set of ExemplarCharacters from
  *   ICU's locale data or other sources
  *
+ * 2. UCNV_ROUNDTRIP_AND_FALLBACK_SET
+ *
+ * The set of all Unicode code points that can be converted with the converter (ucnv_fromUnicode())
+ * when fallbacks are turned on (see ucnv_setFallback()).
+ * This set includes all code points with roundtrips and fallbacks (but not reverse fallbacks).
+ *
  * In the future, there may be more UConverterUnicodeSet choices to select
  * sets with different properties.
  *