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!

Merge branch 'master' of bitbucket.org:ahuelsing/xmss_ref

The bug occured for cases where d=3 and indicated
a lack of updates. Re-implementing the higher-level
structure of BDS resolved this.

Conflicts:
	Makefile
	test/test_chacha
	test/test_wots
	test/test_xmss