[9fans] acme/Mail sorted by replies(threaded)

[Uvelichitel]

        Hi. I know at least one implementation exist before 
https://bitbucket.org/mpl/acmemail-with-sort-by-thread. It based on 
Subject header comparison. So I write another one based on MessageID 
and Inreplayto headers. 
        https://bitbucket.org/uvelichitel/mail
You can mk install. Flag -t added for threading. Tested on p9p.
Fill free to try. Feedback appreciated.
        Best regards.