ifdef-out the asprintf and vasprintf prototypes when building w/non-MSVC

tools (caused build failure on redefinition of functions).

src/xpdev/xpprintf.h

@@ -8,7 +8,7 @@
  * @format.tab-size 4		(Plain Text/Source Code File Header)			*
  * @format.use-tabs true	(see http://www.synchro.net/ptsc_hdr.html)		*
  *																			*
- * Copyright 2006 Rob Swindell - http://www.synchro.net/copyright.html		*
+ * Copyright Rob Swindell - http://www.synchro.net/copyright.html			*
  *																			*
  * This library is free software; you can redistribute it and/or			*
  * modify it under the terms of the GNU Lesser General Public License		*
@@ -79,8 +79,11 @@ DLLEXPORT char* DLLCALL xp_asprintf_end(char *format, size_t *endlen);
 DLLEXPORT char* DLLCALL xp_asprintf(const char *format, ...);
 DLLEXPORT char* DLLCALL xp_vasprintf(const char *format, va_list va);
 DLLEXPORT int DLLCALL xp_printf_get_type(const char *format);
+#if defined(_MSC_VER) || defined(__MSVCRT__)
 DLLEXPORT int DLLCALL vasprintf(char **strptr, char *format, va_list va);
 DLLEXPORT int DLLCALL asprintf(char **strptr, char *format, ...);
+#endif
+
 #if defined(__cplusplus)
 }
 #endif