Rework help interface of vcregress.pl

Hi all,
(Windows-only be careful)

Horiguchi-san has mentioned yesterday
(http://www.postgresql.org/message-id/20160414.172539.34325458.horiguchi.kyotaro@lab.ntt.co.jp)
that we are missing a couple of modes in vcregress.pl in its help
message: modulescheck, bincheck, recoverycheck.

The help message given to users is ugly and unreadable:
$ perl vcregress.pl
Usage: vcregress.pl
<check|installcheck|plcheck|contribcheck|isolationcheck|ecpgcheck|upgradecheck>
[schedule]
So I would like to suggest the attached patch that makes things easier
to understand:
$ perl vcregress.pl
Usage: vcregress.pl <mode> [ <schedule> ]

Options for <mode>:
  bincheck       run tests of utilities in src/bin/
  check          deploy instance and run regression tests on it
  contribcheck   run tests of modules in contrib/
  ecpgcheck      run regression tests of ECPG driver
  installcheck   run regression tests on existing instance
  isolationcheck run isolation tests
  modulescheck   run tests of modules in src/test/modules
  plcheck        run tests of PL languages
  recoverycheck  run recovery test suite
  upgradecheck   run tests of pg_upgrade

Options for <schedule>:
  serial         serial mode
  parallel       parallel mode

Regards,
--
Michael