Build system "fixes", debian/ directory for packaging

These commits include a build system "fix", which is basically a hacky way of generating and installing a .pc file with distutils (I asked python-list for a better way, but got no responses). In any case, we need to generate and install a valid .pc file since py2cairo's (autoconf based) build system requires one to correctly detect xpyb. They have a waf based system, but it doesn't seem to support xpyb.

These commits also include a debian/ subdirectory for packaging purposes (I still don't have py2cairo's packages set up quite correctly, but xpyb-ng seems to work fine).