libinfinity-0.5.2 requires a dependency on :x11 so that pkg-config
can find freetype2 for cairo. Otherwise two libinfinity libraries
will not be created, which will cause other packages that use
libinfinity to fail, like gobby.
Tested on Lion with llvm from XCode-4.3.3.
ClosesHomebrew/homebrew#13416.
Signed-off-by: Misty De Meo <mistydemeo@gmail.com>