Editing of man/repl.com.

- unashamedly add nmh to .SH NAME
- replace the delightfully baroque 'may be used to produce a reply
  to an existing message' with 'may be used to reply to a message'.
- remove some \- objects
- deflower 'repl uses a reply template to guide its actions'
- remove multiple instances of 'replied\-to', with 'replied to'
- change 'tab\-stop' to 'tab stop'
- some formatting
- replace .B mhbuild with .IR mhbuild (1)
- replace whatnow with .B whatnow