Move redundant bits from screen_init (while dealing with existing
clients) directly into client_init, performing the X roundtrip only
once. With the previous change in maprequest, this moves decision making
into one place for creating new clients.
make this XQueryTree like the other
Introduce a region queue and replace screen's XineramaScreenInfo; we
still use Xinerama to populate the regions per screen, but will switch
at a more appropriate time.