Import mdocml-1.12.1
rm(1): Add -x option to prevent recursive rm crossing mount points.

Submitted-by:  Joris Giovannangeli <joris@giovannangeli.fr>
Dragonfly-bug: <http://bugs.dragonflybsd.org/issues/2546>
Merge branch 'vendor/MDOCML'
Add libmandoc.
mandoc(1): Adjust Makefile for 1.12.1.
mandoc.3: Some small fixes.