Decrease cairo req for xcb tests
Decrease cairo req for xcb tests

This should probably be 11200, for cairo 1.12, rather than 12000, which
would be cairo 1.20.  This runs the tests and passes (at least for me),
while still xfailing on the Ubuntu 12.04 cairo that Travis uses.

SimonSapin/cairocffi,makinacorpus/cairocffi,NotBobTheBuilder/cairocffi