Codechange: [OSX] GameLoop is really more like MainLoop

MainLoop() is used to bootstrap OSX, where later a callback is
done to GameLoop() to execute OpenTTD. All other video drivers
don't need that, so what is in GameLoop is in MainLoop for all
other drivers. This is rather confusing. So, instead, name
GameLoop MainLoopReal to be more in sync with the other drivers.

src/video/cocoa/cocoa_wnd.mm

@@ -152,7 +152,7 @@ static std::vector<WChar> NSStringToUTF32(NSString *s)
 	[ e release ];
 
 	/* Hand off to main application code. */
-	drv->GameLoop();
+	drv->MainLoopReal();
 
 	/* We are done, thank you for playing. */
 	[ self performSelectorOnMainThread:@selector(stopEngine) withObject:nil waitUntilDone:FALSE ];