new package to factory.

Neomutt is a fork of mutt and provides same functionality, but wants to be more
open to development and feature rich. The codebase of the two projects has
diverged substantially and it's not feasible to keep neomutt patch hidden
inside our mutt package.

Besides the packaging/patch, the mutt project does not want to see neomutt
patch being applied to mutt and still calling the package 'mutt' by the
distros. This has been made clear when neomutt was added to Debian
(https://marc.info/?l=mutt-users&m=149875493532305&w=2 ,
https://marc.info/?l=mutt-users&m=149886522430053&w=2 ).

The two packages can be installed in parallel and use different config files,
so there is no usability hurdle for existing mutt users.
~