Upgrade to libxml 2.9.2 and libxslt 1.1.28

third_party/libxslt/BUILD.gn

 # Copyright 2014 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.
 
 config("libxslt_config") {
   defines = [ "LIBXSLT_STATIC" ]
   include_dirs = [ "." ]
 }
 
 static_library("libxslt") {
@@ skipping 38 matching lines @@
     "libxslt/xsltInternals.h",
     "libxslt/xsltconfig.h",
     "libxslt/xsltexports.h",
     "libxslt/xsltlocale.c",
     "libxslt/xsltlocale.h",
     "libxslt/xsltutils.c",
     "libxslt/xsltutils.h",
     "libxslt/xsltwin32config.h",
     "linux/config.h",
     "mac/config.h",
+    "win32/config.h",
   ]
 
   configs -= [ "//build/config/compiler:chromium_code" ]
   configs += [ "//build/config/compiler:no_chromium_code" ]
   public_configs = [ ":libxslt_config" ]
 
   if (is_linux || is_android) {
     include_dirs = [ "linux" ]
   } else if (is_win) {
     include_dirs = [ "win32" ]
+    cflags = [ "/wd4267" ]  # size_t to int.
   } else if (is_mac) {
     include_dirs = [ "mac" ]
   }
 
   if (is_clang) {
     cflags = [ "-Wno-pointer-sign" ]
   }
 
   deps = [
     "//third_party/libxml",
   ]
 }