mailutils 2.2 (new formula)

GNU Mailutils is used in the background by various other software packages. For example, GNU Emacs uses it in order to be able to fetch mail over IMAP or TLS.

I couldn't get the Python interface library to build, so I disabled that. Some non-essential programs get installed into `$PREFIX/bin/mu-mh/`, which `brew audit` complains about, so I disabled those too.