mg-troglobit (Portable self hosting version of the mg-openbsd editor)

The intention is to be a small, fast, and portable Emacs-like editor
for users who cannot, or do not want to, run the real Emacs for one
reason or another.

Compatibility with GNU Emacs is key for Mg, separating it from other
ErsatzEmacs clones, because there should never be any reason to learn
more than one Emacs flavor.
