* Adds Python 3 to macOS requirements
* Gate include of `DEPEND_FILE` in `rules.mak` on whether the target is `clean` or not (the include isn't pre-processed; it will attempt to build everything in the include otherwise)
* Make `makedbh` a configurable file- the shebang now uses the discovered path for Python3
This is a series of updates to make building magic far less of a headache:
* Drop `csh`/`tcsh` dependency and detection from `./configure`.
* Rewrite makedbh in Python.
* Rewrite printmans in POSIX sh.
* Stop deleting Depend before every compile (which causes some files to recompile and thus increases recompile times significantly)
* Add Depend to CLEANS in scripts/defs.mak.in
* Turn POSIX suffix rule in magic/rules.mak to a pattern rule with proper prerequisites
Donn