Using global defines for parameters (as seems to be typical in
academic crypto code) does not play nice with multithreading at all.

This also performs numerous consistency fixes

A large number of functions was repeated in xmss_fast; these are now
shared between the two implementations via the xmss_commons file.
Notably, we ensure compatability by sharing the verification functions.

This starts a cleanup / refactor, but there is still some low-hanging fruit.

Versions are incompatible due to different address formats and differing message compression!