wlfreerdp: add keyboard and mouse wheel support, fix bugs

This commit does the following:

* fix the keyboard logic (which now fully works), add support for vertical mouse wheel events ;
* make the rendering a lot more efficient, by using RDP damage information to refresh only the relevant part of the buffer ;
* fix two race conditions. wlfreerdp should not crash anymore now ;
* fix shm_open() and shm_unlink() calls ;
* improve the code style.

Signed-off-by: Manuel Bachmann <tarnyko@tarnyko.net>
Merge pull request #2232 from Tarnyko/master

wlfreerdp: add keyboard and mouse wheel support, fix bugs