[Bug 58893] Window caption updates have huge delay

[WineHQ Bugzilla]

http://bugs.winehq.org/show_bug.cgi?id=58893

--- Comment #3 from Rémi Bernon  ---
It wasn't necessary because we used to check for events regularly even without
anything to read from the X pipe. Xlib automatically flushes the output pipe as
long as events are being checked.

Now, with the refactoring for ntsync, we instead let wineserver poll the X pipe
and notify the client side when events are ready to be read, notifying
wineserver back when all events have been processed so it starts polling again.

The client doesn't check for events needlessly anymore, but that also means
that Xlib won't be able to flush output automatically in some cases (we do it
*after* draining the events but that's sometimes not enough) and until we add
some mechanism to poll for output too, we now need to flush requests explicitly
when they are issued outside of ProcessEvents and if their effect is meant to
be immediate visible.