doc: Revise sec:matchrules.
Fix a compatibility issue with LuaTeX 0.70.2.

With LuaTeX 0.70.2, field user_id of user_defined whatsit nodes
needs to be less than 2^31.  In case user id management per package
luatexbase-attr isn't available, utilised user IDs now start at a
value of 13^8 (ca. 2^30).
Fix: Explicitly load package luatexbase-mcb.
doc: Revise lst:mr-bibtex-alpha.

Cover the case of Surenames consisting of only two letters.
Update version number.