client: Add mediated reader stopping for display proxy
Add display API for negotiated display event reader's early exits.
Closes #28
This patch allows display event readers to exit their polling and processing loops early based on when something calls wl_display_stop.
TODO: There is still a potential issue of new threads starting after wl_display_stop has returned, which would need a more significant change to give the display API control of the display pointer, and check whether it is nulled before dereferencing throughout the current API.
Signed-off-by: Robert Beckett bob.beckett@collabora.com