use g_free() instead of free()

On some platforms, g_free() must be used for memory allocated by
GLib.  This patch intends to correct a lot of occurrences, but is
probably not complete.

src/decoder/mikmod_plugin.c

@@ -152,7 +152,7 @@ static void mod_close(mod_Data * data)
 {
 	Player_Stop();
 	Player_Free(data->moduleHandle);
-	free(data);
+	g_free(data);
 }
 
 static void