vs2015: Don't have posix error codes defined during libxml build

third_party/libxml/README.chromium

Index: third_party/libxml/README.chromium
diff --git a/third_party/libxml/README.chromium b/third_party/libxml/README.chromium
index f12d267a34467f65d3f56ebddedcbd0126595b91..6d1ab44e9967736254b4f4c925eebc87adb68cbc 100644
--- a/third_party/libxml/README.chromium
+++ b/third_party/libxml/README.chromium
@@ -29,14 +29,15 @@ Modifications:
 - Add helper classes in chromium/libxml_utils.cc and chromium/include/libxml/libxml_utils.h.
 - Add a tweak to limit problems caused by excessive strings and buffers.
 - Change the xmlNs struct a little bit, so it looks like it has no children
-- Prevent snprintf from being defined as _snprintf on VS 2015.
-if treated as a generic xmlNode object.
+  if treated as a generic xmlNode object.
 - Fix pretty harmless use-after-free in generate-id function.
 - Merge a clang warning fix http://git.gnome.org/browse/libxml2/commit/?id=713434d2309da469d64b35e163ea6556dadccada
 - Import attribute normalization fix http://git.gnome.org/browse/libxml2/commit/?id=6a36fbe3b3e001a8a840b5c1fdd81cefc9947f0d
 - Merge a redundant comparison fix http://git.gnome.org/browse/libxml2/commit/?id=2af19f985b911b6dc6ada478ba8d201d2ddc9309
 - Merge a redundant comparisons fix https://git.gnome.org/browse/libxml2/commit/?id=eea38159be421dbafbee38f40e239f91734bc713
 - Merge XML_PARSER_EOF checks https://git.gnome.org/browse/libxml2/commit/?id=48b4cdde3483e054af8ea02e0cd7ee467b0e9a50 and https://git.gnome.org/browse/libxml2/commit/?id=e50ba8164eee06461c73cd8abb9b46aa0be81869
+- Prevent snprintf from being defined as _snprintf on VS 2015.
+- Make ucrt of Win10 SDK not define POSIX error codes.
 
 To import a new snapshot of libxml: