Upgrade to libxml 2.9.2 and libxslt 1.1.28

third_party/libxml/libxml.gyp

 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 {
   'variables': {
     'conditions': [
       # Define an "os_include" variable that points at the OS-specific generated
       # headers.  These were generated by running the configure script offline.
       ['os_posix == 1 and OS != "mac" and OS != "ios"', {
@@ skipping 114 matching lines @@
             'src/include/libxml/xmlschemastypes.h',
             'src/include/libxml/xmlstring.h',
             'src/include/libxml/xmlunicode.h',
             'src/include/libxml/xmlwriter.h',
             'src/include/libxml/xpath.h',
             'src/include/libxml/xpathInternals.h',
             'src/include/libxml/xpointer.h',
             'src/include/win32config.h',
             'src/include/wsockcompat.h',
             'src/acconfig.h',
+            'src/buf.c',
+            'src/buf.h',
             'src/c14n.c',
             'src/catalog.c',
             'src/chvalid.c',
             'src/debugXML.c',
             'src/dict.c',
             'src/DOCBparser.c',
             'src/elfgcchack.h',
             'src/encoding.c',
             'src/entities.c',
             'src/error.c',
@@ skipping 111 matching lines @@
             }],
           ],
         }],
         ['OS == "ios"', {
           'toolsets': ['host', 'target'],
         }],
       ],
     },
   ],
 }