Serial ports redirection based on winpr-comm

* Started implementation of winpr-comm
* channels/serial rewritten and based on winpr-comm

Just a few modifications beside libwinpr/comm/* and channels/serial/*
* libwinpr/file/file.c: added RegisterHandleCreator(...)
* libwinpr/handle/handle.c: added RegisterHandleCloseCb(...)
* winpr/inlcude/wlog/wlog.h: exported WLog_PrintMessageVA() and defined WLog_PrintVA()


Notes: 

1. The whole winpr-comm's API have not been implemented yet. However especially considering the SerCx2.sys' requirements only, I think enough has been done to support most of the serial devices and to have significantly improved the previous implementation of the serial ports redirection.

2. Nothing has been done about the parallel port redirection.

3. See remaining TODO and FIXME tags in the code, supporting the Special Characters could be an easy next step.

4. The implementation is not validated by a significant amount of actual devices yet.