Removes some cairo/cairocks shared code.

I attempted to create a shared extension type between the cairo and
cairocks modules created by Cython, but after following the instructions
to the letter, it still wouldn't work. Cython is decent, but there are
many cases in which it sucks balls so massive I want to never touch it
again. I'm going to just stop trying for now, because it is simply
wasting too much of my time.