Roll libxml to 2.9.3

third_party/libxml/win32/config.h

Index: third_party/libxml/win32/config.h
diff --git a/third_party/libxml/win32/config.h b/third_party/libxml/win32/config.h
index 40cf7df8047f4e6fdacd06e677dccd1faf71fd73..8629944e6e2a0ca86d94592d8e49162680e6265b 100644
--- a/third_party/libxml/win32/config.h
+++ b/third_party/libxml/win32/config.h
@@ -5,8 +5,7 @@
 #define HAVE_STDARG_H
 #define HAVE_MALLOC_H
 #define HAVE_ERRNO_H
-#define SEND_ARG2_CAST
-#define GETHOSTBYNAME_ARG_CAST
+#define HAVE_STDINT_H
 
 #if defined(_WIN32_WCE)
 #undef HAVE_ERRNO_H
@@ -97,9 +96,7 @@ static int isnan (double d) {
 
 #if defined(_MSC_VER)
 #define mkdir(p,m) _mkdir(p)
-#if _MSC_VER < 1900
 #define snprintf _snprintf
-#endif

[Peter Kasting, 2016/03/03 22:32:53]

Removing these two lines is what broke the Visual Studio 2015 build.  If they
are restored, things build correctly.

AFAICT, upstream has both include/win32config.h and win32/VC10/config.h, which
are almost identical except that the latter is missing this change, and there
are minor differences in the #defines atop the files.  The deltas in this patch
set suggest we moved from this being a copy of the former to a copy of the
latter.  I'm not sure whether that's correct.

Honestly, I don't understand precisely what upstream intends the differences
here to be.  I suspect it is an error to have both of these files and have them
only slightly different.  Probably upstream needs to just use one, from one
place.

 #if _MSC_VER < 1500
 #define vsnprintf(b,c,f,a) _vsnprintf(b,c,f,a)
 #endif