mplayer: potentially fix main() return value

The main() function is special, and omitting the return statement would
make it always return 0. And also, mpv_main() actually never returns, it
calls exit() through exit_player() instead. But change it anyway,
because it looks misleading.

core/mplayer.c

@@ -4773,9 +4773,9 @@ static int mpv_main(int argc, char *argv[])
 int main(int argc, char *argv[])
 {
 #ifdef CONFIG_COCOA
-    cocoa_main(mpv_main, argc, argv);
+    return cocoa_main(mpv_main, argc, argv);
 #else
-    mpv_main(argc, argv);
+    return mpv_main(argc, argv);
 #endif
 }