Xi: Do not try to swap GenericEvent.

The SProcXSendExtensionEvent must not attempt to swap GenericEvent because
it is assuming that the event has fixed size and gives the swapping function
xEvent-sized buffer.

A GenericEvent would be later rejected by ProcXSendExtensionEvent anyway.

Signed-off-by: Michal Srb <msrb@suse.com>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
(cherry picked from commit ba336b24)