import mdocml 1.13.3

Merge mdocml state from 2012-01-30 for various relaxed checks in the
parser to allow it to pass almost all man pages in pkgsrc.

Import mdocml 1.12.0:
- Support to output HTML fragments
- Initial support for mdoc->man translation
- Initial eqn support
- preconv / apropos / demandoc (not hooked up)
- Various bugfixes