This change updates Babel decoder output format to match terminology of
draft-ovsienko-babel-hmac-authentication-00 and reverts recent addition
of DLen field to TLV type 12.
This change reflects a new Digest Length field added to Hash Digest TLV
in the current draft of Babel authentication spec. babel_print_v2() is
updated to fetch and validate the new field. Test files too.
This change extends existing Babel protocol decoder to recognise
experimental authentication TLVs (types 11 and 12) and includes
a respective test case for the new code.
