mh-e-user-agent to use mh-user-agent-compose, mh-smail-batch deprecated

[Bill Wohler]

I'm updating mh-e-user-agent in simple.el to use mh-user-agent-compose
as it conforms to the contract defined by define-mail-user-agent. I'll
delete the old compose function mh-smail-batch when we no longer support
Emacs 21.

While I'm at it, I might as well move the definition of mh-e-user-agent
to mh-comp.el and add an ;;;###autoload cookie for it, like Gnus.

-- 
Bill Wohler <address@hidden>  http://www.newt.com/wohler/  GnuPG ID:610BD9AD
Maintainer of comp.mail.mh FAQ and MH-E. Vote Libertarian!
If you're passed on the right, you're in the wrong lane.