mail/mu: Improve port and fix compatibility with (lib)fmt 12
- Switch to upstream release archive
- Backport upstream patch 0a4fabbf446d15b538600dfe7d879cad70ce941e for comptibility with (lib)fmt 12
- Make MANPAGES optional (removes build dependency of emacs)
- Drop info files to simplify port
- Define SHEBANG_FILES as we're only patching a single file
- Sort options and related variables in port Makefile
References:
https://github.com/djcb/mu/commit/0a4fabbf446d15b538600dfe7d879cad70ce941e
PR: 290616
Reviewed by: RwN <rwn@mailo.com> (maintainer)