[xml] problem with MinGW and standard C headers

[<oliverst online de>]

I recently changed all the standard C headers to the new ones (<stdio.h>
-> <cstdio>) and now I got a problem when compiling my source:

167 C:\MinGW_3.4.2\include\c++\3.4.2\cstdio `::snprintf' has not been
declared 
170 C:\MinGW_3.4.2\include\c++\3.4.2\cstdio `::vsnprintf' has not been
declared 
177 C:\MinGW_3.4.2\include\c++\3.4.2\cstdio `__gnu_cxx::snprintf' has
not been declared 
180 C:\MinGW_3.4.2\include\c++\3.4.2\cstdio `__gnu_cxx::vsnprintf' has
not been declared 

I reduced the source giving me this problem to the following:

#include "libxml/win32config.h"
#include <cstdio>

The problem is the #define of snprintf and vsnprintf in there for MinGW.
It's not available in the old style headers, but in the new ones.
Removing the two defines from "win32config.h" fixes the problem. I am
not sure how to properly fix it.