Global auto-away

Implements desktop-wide auto-away (like in skype/pidgin/others).

Be aware:
MacOS code was not tested, i would love if anyone could test it before merging!
X11 part works ok for me.
Windows part not tested but there isnt much room for mistakes.

Also someone knowledgeable please verify qtox.pro, i am not sure i added dependencies properly. No idea what to link for macs, not sure if x11 deps are in correct spots, not sure if user32 is linked in auto or we need to add dependency manually.

Also now timer checks for system idle time every 10 seconds. It works but if anyone have better ideas i would love to hear them.

I would love some feedback on all of this ;)