API change: added void *user_data to mg_start(). Bumped version to 3.0

test/embed.c

@@ -167,7 +167,7 @@ int main(void) {
 	struct mg_context	*ctx;
   const char *options[] = {"listening_ports", LISTENING_PORT, NULL};
 
-	ctx = mg_start(callback, options);
+	ctx = mg_start(callback, NULL, options);
   pause();
   return 0;
 }