Merge branch 'bs/stdio-undef-before-redef'

When we replace broken macros from stdio.h in git-compat-util.h,
preprocessor.

* bs/stdio-undef-before-redef:
  git-compat-util.h: #undef (v)snprintf before #define them

git-compat-util.h

@@ -480,9 +480,15 @@ extern FILE *git_fopen(const char*, const char*);
 #endif
 
 #ifdef SNPRINTF_RETURNS_BOGUS
+#ifdef snprintf
+#undef snprintf
+#endif
 #define snprintf git_snprintf
 extern int git_snprintf(char *str, size_t maxsize,
 			const char *format, ...);
+#ifdef vsnprintf
+#undef vsnprintf
+#endif
 #define vsnprintf git_vsnprintf
 extern int git_vsnprintf(char *str, size_t maxsize,
 			 const char *format, va_list ap);