Xi: Verify all events in ProcXSendExtensionEvent.

The requirement is that events have type in range
EXTENSION_EVENT_BASE..lastEvent, but it was tested
only for first event of all.

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 8caed4df)