[BRLTTY] PATCH: Switch to cython for building python bindings.

[Jason White]

timothyhobbs at seznam.cz <timothyhobbs at seznam.cz> wrote:
> It's currently very important that Python 2 remain supported, as Orca uses
> Python 2!

Yes, but note that the master branch of Orca has moved to Python 3. Orca 3.6.x
will still use Python 2, but the plan announced on the Orca list was to switch
to Python 3 immediately after 3.6.