Fixed particular slowdown in OS X startup window

During loading of .pk3 that stores hundred of .wad's significant amount of time were spent on scrolling text to the last line
The same applies to other cases like output of thousands warnings/errors

src/posix/cocoa/st_console.mm

@@ -312,10 +312,11 @@ void FConsoleWindow::AddText(const char* message)
 	}
 
 	if ([m_window isVisible])
+	{
+		UpdateTimed([&]()
 		{
 			[m_textView scrollRangeToVisible:NSMakeRange(m_characterCount, 0)];
-
-		[[NSRunLoop currentRunLoop] limitDateForMode:NSDefaultRunLoopMode];
+		});
 	}
 }