Remove FScreenConfigureModule / FScreenGetConfiguration

Modules relying on monitor-specific information will be configured locally, and
module packets sent to modules will instead receive the monitor such events
occurred on.
Officially deprecate Xinerama / XineramaPrimaryScreen

These no longer make sense with XRandR; may well be resurrected in some other
guise later on.

For now the commands exist as stubs only, with a deprecation warning present
until such time that we deal with configuration migration properly.