Fix vasprintf fallback

Once a va_list has been processed, it cannot be used again. Make a
copy and use it for the initial call to determine the string length.

vasprintf_compat.h

@@ -19,24 +19,27 @@ static int vasprintf(char **buf, const char *fmt, va_list ap)
 #endif /* !defined(WIN32) */
 	int chars;
 	char *b;
+	va_list ap2;
 
 	if (!buf)
 	{
 		return -1;
 	}
 
+	va_copy(ap2, ap);
 #ifdef WIN32
-	chars = _vscprintf(fmt, ap) + 1;
+	chars = _vscprintf(fmt, ap2) + 1;
 #else  /* !defined(WIN32) */
 	/* CAW: RAWR! We have to hope to god here that vsnprintf doesn't overwrite
 	 * our buffer like on some 64bit sun systems.... but hey, its time to move on
 	 */
-	chars = vsnprintf(&_T_emptybuffer, 0, fmt, ap) + 1;
+	chars = vsnprintf(&_T_emptybuffer, 0, fmt, ap2) + 1;
 	if (chars < 0)
 	{
 		chars *= -1;
 	} /* CAW: old glibc versions have this problem */
 #endif /* defined(WIN32) */
+	va_end(ap2);
 
 	b = (char *)malloc(sizeof(char) * chars);
 	if (!b)