Update expat to 2.2.0 to fix CVE vulnerability.

third_party/expat/files/lib/internal.h

 /* internal.h
 
    Internal definitions used by Expat.  This is not needed to compile
    client code.
 
    The following calling convention macros are defined for frequently
    called functions:
 
    FASTCALL    - Used for those internal functions that have a simple
                  body and a low number of arguments and local variables.
@@ skipping 53 matching lines @@
 #endif
 #endif /* XML_MIN_SIZE */
 
 #ifdef __cplusplus
 #define inline inline
 #else
 #ifndef inline
 #define inline
 #endif
 #endif
+
+#ifndef UNUSED_P
+# ifdef __GNUC__
+#  define UNUSED_P(p) UNUSED_ ## p __attribute__((__unused__))
+# else
+#  define UNUSED_P(p) UNUSED_ ## p
+# endif
+#endif
+
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+
+void
+align_limit_to_full_utf8_characters(const char * from, const char ** fromLimRef);
+
+
+#ifdef __cplusplus
+}
+#endif