We delayed the update of cairo to the 1.12 series as long as we possibly
could, but 1.10 was blocking updates to other ports, e.g. pango and gtk30.
Continued availability of cairo 1.10 would prevent building of any GTK+
applications.
Cairo 1.12 exposes some driver bugs in xf86-video-intel 2.7.1, and may expose
bugs in other older drivers. These bugs manifest as display artifacts.
Conversely, this update fixes some graphical glitches with xorg-server 1.12.
