Support multiple ListenAddress ports

Reported by:	rustamabd@gmail.com
Upgrade from 3.7.24 to 6.0.27.
- Mark OVERWRITE_BASE and security/openssh-portable-base as DEPRECATED.
  These will be removed on January 1 2015.

  Really ports should not be touching the base system at all.

  This option is a big foot-shoot problem:

  1. Recent versions of FreeBSD such as 9.3, 10.0, 10.1+, now remove all ssh
     files from /usr if you 'make delete-old' with WITHOUT_SSH. This results in
     removing the overwrite base files.
  2. Uninstalling the package leaves the system with no ssh.
  3. Running installworld without WITHOUT_SSH results in overwriting the
     package, or giving false-positive 'pkg check -s' errors.
  4. The port fails to pass QA checks because it removes system files.
Make sure, ${PREFIX}/etc/ is searched for config-files, rather than the
/etc
- Replace USE_AUTOTOOLS with USES=autoreconf
- Move BUILD_DEPENDS up