Update LaTeX, \rm -> \mathrm (#3039)

* Update LaTeX, \rm -> \mathrm

Per #3037, update the LateX to change from the deprecated \rm
to the official \mathrm{...}.

I started this using this regular expression:
sed -E -i '' -e '/latexdef/s/\\rm (\\?[A-Za-z0-9\-^\.\[\]\;]+) *\}/\\mathrm{\1}}/g' set.mm iset.mm

.. and then fixed others by hand. I fixed all the entries in
set.mm, and many in iset.mm. If this approach seems reasonable we can fix
the rest of iset.mm.

* Fix long lines

* Remove unnecessary {..} around TeX \methrm

In TeX, \mathrm{...} is a single unit.

This removes the unnecessary {...} surrounding them in many cases.
This was done by:

~~~~sh
sed -E -e 's/\{\\mathrm\{([A-Za-z0-9;\\</#]+)\}\}/\\mathrm\{\1\}/g' set.mm \
  > ,set
mv ,set set.mm
~~~~~

Signed-off-by: David A. Wheeler <[email protected]>

* Remove unnecessary {...} in TeX on iset.mm

Signed-off-by: David A. Wheeler <[email protected]>