Miscellaneous improvements to configure.

Miscellaneous improvements to configure.

- Clean up various minor sections of the code.
- Remove OpenSSL and GnuTLS detection plumbing.
  - This will soon be the job of modulemanager.
  - This did not work in non-interactive mode unlike --enable-extras.
- Rework runas user handling.
  - Add the --gid configure option.
  - Accept either an id or a name in --gid and --uid.
- Rework the question flow in interactive mode.
  - User is no longer asked detailed questions unless they want them.
  - Socket engine questions have been removed.
- Automatically enable non-interactive mode if STDIN or STDOUT are not
  a tty.