xdo_get_window_location uses the X11 Screen struct instead of the screen index

[KoFish]

Other functions dealing with screens in libxdo uses only the integer index of screens while xdo_get_window_location returns X11's Screen structure, and only if the caller wants it. This breaks the convention used otherwise in the library.

[jordansissel]

I think I prefer returning a Screen (for all functions), do you have a preference?

[KoFish]

My life becomes much simpler if all functions returns the index of the screen. Anytime I need a Screen I can do that Xlib call (XScreenOfDisplay I assume) rather than always having to deal with a pointer I don't need.