- add Korean input.
- add IME support in text object, console, text editor, uibutton.
- improve input quality.
In my test, this patch makes IME can input text like other programs supporting IME.
I'm new at making a patch, so I may have make a mistake when writing code.
But I think it can help to implement IME support.
IME in text object will show composition window on cursor to show the progress of the input.
Now this patch will only implement Korean input in button text on Windows, and improve the ime event handling method.