make event loop simpler (Thanks to Jamey Sharp)

make event loop simpler (Thanks to Jamey Sharp)

As explained in Jamey’s post on the XCB mailing list, the event
loop can/should be written in a more simple way than it was before
in xcb-event. See:
<AANLkTinhIM320wUjSeHkBTVk4ysBuiSZkvfs8pMLVykO@mail.gmail.com>
or
http://lists.freedesktop.org/archives/xcb/2010-July/006292.html