[patch] fix ATSUI support, fix CJK (wide) character rendering, fix TSM support

Hi,

The patch attach fixed the following stuff:

1. Use kATSUImposeWidthTag to set font width equal to gui.char_width. This
makes sure offset calculation in ATSUI rendering is correct.

2. Use a different style object called gWideFontStyle to support CJK character
rendering, which must be 2 * gui.char_width in width.

3. Add NewTSMDocument, ActivateTSMDocument in gui_mch_init() to improve
Text Service Manager (for Input Method) support.

Please review and test it as needed. It will be a great help to most CJK gvim
users if this patch can be merged into trunk. ;)

- jjgod.