[Xcb] An X input method protocol implementation in xcb

[Weng Xuetian]

Hi xcb world,

I just implemented a library which can be used to implement either xim server 
and client. Initially I just want to implement a server support so the imdkit 
name comes from the Xlib's imdkit, but finally I end up with a complete 
server/client support for xim protocol.

It's just being roughly implemented and it's not well tested yet. But there is 
already some obvious benefit against old xlib implementation:
1. avoid quite a lot memory copy 
2. async to prevent a dead wait on xim server failure
3. application developer can explicitly send event to xim server instead of 
using xlib event filter.

And I think some toolkit might be interested to make some use of it, like qt 
and sdl who already moved to xcb but without X input method support.

In future I might add xinput2 event support to it as a new extension. And I 
already planned to use the server part in fcitx.

Code and be obtained here:
https://github.com/wengxt/xcb-imdkit

I've played with test_server and xterm in Xephyr and it works as expected.
Your comments are welcome, thanks!

Regards,
Xuetian