bsdtextproc week #8

[Ben Fiedler]

This past week I worked on the logic for the diff format processing.  These
switches are still is a work-in-progress, and I expect to implement them in
a discrete manner throughout the next few weeks. I  am hoping that moving
forward will give me fresh eyes on return to the problem.
 In the meantime, for this week I am proceeding to the next milestone; mdoc
into the base! Branch is ready, and I am merging with Ulrich's changes.
This week, I hope to 1.) modify the build system to allow for replacing
groff with mandoc via some boolean define (perhaps WITH_MANDOC ?) so that
users may opt-in,    2.) Identify any build errors from 1 in relation to man
pages or dependent tools (e.g. old, mandoc-incompatible man pages), and
attempt to resolve with an alternate, supplemental man repository or more
makefile mods.

-Ben