convert: deprecate --authors in preference for --authormap
This aligns the authormap option with the other three mapping options.
The old --authors option is still supported and 'hg help convert -v'
will still show it.
Basic install:
$ make # see install targets
$ make install # do a system-wide install
$ hg debuginstall # sanity-check setup
$ hg # see help
See http://mercurial.selenic.com/ for detailed installation
instructions, platform-specific notes, and Mercurial user information.