A working debian package!

There are two remaining warnings, which are harmless,

* One from dpkg-shlibdeps about the generated cffi shared object linking
  against libpthread. We can't fix this because it is cffi doing the code
  generation and linking.
* One about an unused variable ${python:Versions}. This is unused, viz:
  https://lists.debian.org/debian-python/2012/05/msg00067.html