[referencer] Python Dependency

[Aaron Seilis]

Hey all,

I've been going through the build process and I'm wondering whether
Python is meant to actually be optional or not. I've found that with the
code as-is, it can't actually be compiled without Python (even with
Python disabled).

Regardless, on my system, I had to update configure.ac to add Python to
pkg-config for it to compile and run.

If everyone is comfortable with Python as a dependency, I will remove
the autoconf conditional tests and add Python to pkg-config.

Aaron