Add tex requirement

* Detect `latex' and `bibtex' commands.
* Recommend installing MacTeX when no LaTeX installation is found.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>
Enable LaTeX support in gnuplot.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>
Make auctex use TeX requirement.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>
Make asymptote use TeX requirement.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>
Make latex-mk use TeX requirement.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>
Make lilypond use TeX requirement.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>
Make chktex use TeX requirement.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>
Make pdfjam use TeX requirement.

Closes #16568.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>