glx: Fix __glXWireToEvent for BufferSwapComplete

glx: Fix __glXWireToEvent for BufferSwapComplete

In the DRI2 path this event is magically synthesized from the
corresponding DRI2 event, but with Present, the server sends us the
event itself. The DRI2 path fills in the serial number, send_event, and
display fields of the XEvent struct that the app sees, but the Present
path did not.

This is likely related to a class of crashes seen in gtk/clutter apps:

https://bugzilla.redhat.com/attachment.cgi?id=1032631

Note that the crashing instruction is looking up the lock_fns slot in
the Display *, and %rdi (holding the Display *) is 0x1.

Cc: mesa-stable@lists.freedesktop.org
Signed-off-by: Adam Jackson <ajax@redhat.com>
Reviewed-by: Eric Anholt <eric@anholt.net>