Log Message:
Update libXi to 1.7.6.

One significant change here: libXi was using raw serial numbers in event
cookies, the one read off the wire. All other events don't use that number
but a Xlib-internal serial number which is similar but not always the same.
This could cause events to look out of order. With this release, libXi is
now using the same serial number for event cookies as it uses for all other
events.

Javier Pello (1):
      Fix const compiler warnings

Peter Hutterer (2):
      Don't use raw serial numbers in XIEvents
      libXi 1.7.6