Update expat to 2.2.0 to fix CVE vulnerability.

third_party/expat/files/README

 
-                        Expat, Release 2.1.0
+                        Expat, Release 2.2.0
 
 This is Expat, a C library for parsing XML, written by James Clark.
 Expat is a stream-oriented XML parser.  This means that you register
 handlers with the parser before starting the parse.  These handlers
 are called when the parser discovers the associated structures in the
 document being parsed.  A start tag is an example of the kind of
 structures for which you may register handlers.
 
 Windows users should use the expat_win32bin package, which includes
 both precompiled libraries and executables, and source code for
@@ skipping 94 matching lines @@
 2) in-makefile
 3) environment  
 
 Note: This only applies to the Expat library itself, building UTF-16 versions
 of xmlwf and the tests is currently not supported.         
 
 Note for Solaris users:  The "ar" command is usually located in
 "/usr/ccs/bin", which is not in the default PATH.  You will need to
 add this to your path for the "make" command, and probably also switch
 to GNU make (the "make" found in /usr/ccs/bin does not seem to work
-properly -- appearantly it does not understand .PHONY directives).  If
+properly -- apparently it does not understand .PHONY directives).  If
 you're using ksh or bash, use this command to build:
 
         PATH=/usr/ccs/bin:$PATH make
 
 When using Expat with a project using autoconf for configuration, you
 can use the probing macro in conftools/expat.m4 to determine how to
 include Expat.  See the comments at the top of that file for more
 information.
 
 A reference manual is available in the file doc/reference.html in this
 distribution.
 
 The homepage for this project is http://www.libexpat.org/.  There
 are links there to connect you to the bug reports page.  If you need
 to report a bug when you don't have access to a browser, you may also
 send a bug report by email to expat-bugs@mail.libexpat.org.
 
 Discussion related to the direction of future expat development takes
 place on expat-discuss@mail.libexpat.org.  Archives of this list and
 other Expat-related lists may be found at:
 
         http://mail.libexpat.org/mailman/listinfo/