win32: use lib system() instead of our own function

mingw32 has system() function, so we don't need our own implementation
anymore.

Signed-off-by: Enrico Weigelt, metux IT consult <info@metux.net>

xkb/ddxLoad.c

@@ -184,7 +184,7 @@ RunXkbComp(xkbcomp_buffer_callback callback, void *userdata)
 #ifndef WIN32
         if (Pclose(out) == 0)
 #else
-        if (fclose(out) == 0 && System(buf) >= 0)
+        if (fclose(out) == 0 && system(buf) >= 0)
 #endif
         {
             if (xkbDebugFlags)