Bug#778650: freerdp-x11: Alt key gets "stuck" with -grab-keyboard option when using Alt-Tab to switch between local X windows

[Vladimir K]

I've tested this patch on jessie. Judging by the description, it should release 
all keys if client loses focus.
But it does not help with stuck Super key in RDP session (when windows are 
switched by Super+Tab on local host). When switching back, Super key is still 
pressed on remote host).