Fix Python 3 build

• While I'm here, convert to options dependency helper

This port is ready for Python 3.
The only failure for FreeBSD (autoplist) is the missing _speedups.so.
Upstream disabled the speedups C extension on Python 3.3+ which fixes the problem.

Obtained from: https://github.com/edgewall/genshi/commit/cef2c8df44166195e1705638f9f17033a4943bb7
With hat: python