Revert "Main: run the OS X native event loop"

This reverts commit f0be48ff90
(except for the NEWS entry).

If libdispatch (GCD) is used before forking, it
can't safely be used again after forking.

src/Main.cxx

@@ -401,8 +401,6 @@ int main(int argc, char *argv[])
 {
 #ifdef WIN32
 	return win32_main(argc, argv);
-#elif __APPLE__
-	return osx_main(argc, argv);
 #else
 	return mpd_main(argc, argv);
 #endif