In looking for `Sm' violators, I found that `Bd -unfilled' or `Bd 
-literal' are playing ugly with mandoc and sub-macros.

The following at least brings us in line with old groff (less some 
spacing issues here and there).  New groff is completely different.  Sigh.

Ingo, this is mostly for you.  Thoughts?  This at least fixes the main 
violators, like awk.1, but there could be unexpected fallout.  I haven't 
been able to find any, but I didn't look too hard.

Kristaps