Add a function, that schedules the display_run() event loop to break
out.
When display_exit() is called, processing continues as usual, until
currently waiting events and deferred tasks have been processed, and
sent requests are flushed. Then, display_run() will return.
This enables toytoolkit apps to handle their exit instead of just being
killed or call exit().
Signed-off-by: Pekka Paalanen <ppaalanen@gmail.com>
Pekka Paalanen
826d795448