libX11: Changes to 'handoff'

[Keith Packard]

 src/Xxcbint.h  |    7 +++++++
 src/xcb_disp.c |    2 ++
 src/xcb_io.c   |   18 ++++++++++++++----
 3 files changed, 23 insertions(+), 4 deletions(-)

New commits:
commit 1cfce69bf65d9631a72f8b20d637bf158c0afd20
Author: Keith Packard <keithp at keithp.com>
Date:   Sat Oct 11 21:10:23 2008 -0700

    Permit only one Xlib thread to block waiting for events
    
    As Xlib queues events internally, we must prevent multiple Xlib threads from
    entering XCB to wait for an event in case the queued event is to be
    delivered to the thread which didn't manage to read it. In other words, let
    only one Xlib thread into xcb_wait_for_event at a time.
    
    Jamey Sharp looked over my shoulder while making this fix and, while hating
    my whitespace conventions, appears happy enough with the actual code.
    
    Signed-off-by: Keith Packard <keithp at keithp.com>