Linux Support via gtk / wnck

[ZereoX]

Hi,

I mainly threw this together for myself, but though I would share in case someone was interested. This PR provides support for Linux by providing a fallback option for win32gui and its underlying window information logic. This should hopefully :crossed_fingers: work for anyone on an X environment.

Changes:

• Only import win32gui on Windows platforms
• Import GTK / Wnck on Linux platforms.
• get_poe_window_info() now pulls screen information from Wnck if the application is running under Linux.

I've marked this as a Draft since its not been tested on Windows and also to gauge interest in merging. I also haven't tested everything so its possible something else might break.

[4rtzel]

Thank you for sharing this. It surprises me how easy it was to port this (judging by the code).