Clean up some markup cruft. A number of the macros that take no

Clean up some markup cruft.  A number of the macros that take no
parameters (like \UNIX) are commonly entered using an empty group to
separate the markup from a following inter-word space; this is not
needed when the next character is punctuation, or the markup is the
last thing in the enclosing group.  These cases were marked
inconsistently; the empty group is now *only* used when needed.