(sit_for): Reduce number of args from 5 to 3.

(sit_for): Reduce number of args from 5 to 3.
Now just one TIMEOUT arg that can be a Lisp float or Lisp int.
Combine args DISPLAY and INITIAL_DISPLAY into one arg DO_DISPLAY.
Undo 2006-06-14 change for non-preemptive display if TIMEOUT < 0.
The rework of sit_for args also fixes several incorrect Qt args
which should have been 1.
(Fredisplay): Pass 1 instead of Qt to swallow_events and
detect_input_pending_run_timers.