x11-libs/cairo: Add explicit dep to media-libs/mesa-9.2.0-r1

x11-libs/cairo-1.12.16-r1 is depending against media-libs/mesa with
MULTILIB_USEDEP use dependencies. On portage the first version that
supports these dependencies is mesa-9.2.0-r1. Hence it makes sense to
add an explicit dependency for cairo to require 9.2.0-r1.

Without this patch portage wanted me to downgrade mesa to 9.0.3 and
giving me slot conflicts. With this patch, it prompts me to unmask
mesa-9.2.0-r1 and after that continues nicely.
Fix app-misc/geoclue Manifest checksums

The file checksums for geoclue-*.tar.xz seem to be wrong for some
reason. I've refreshed the checksums by recreating the Manifest.
Version bump x11-libs/gtk+-2.24.21-r1

Portage version of gtk+:2 is up to 2.24.21 so I've merged the multilib
changes from 2.24.20-r1 to it and bumped it up to 2.24.21-r1.
Merge pull request #4 from mrpdaemon/gtk+2-bump

Version bump x11-libs/gtk+-2.24.21-r1
Merge pull request #3 from mrpdaemon/geoclue-manifest

Fix app-misc/geoclue Manifest checksums
Merge pull request #2 from mrpdaemon/cairo-multilib

x11-libs/cairo: Add explicit dep to media-libs/mesa-9.2.0-r1
graphite2 from FireBurn overlay, solves issue #1