Remove most local modifications from OpenSSH.

Remove most local modifications from OpenSSH.

This primarily removes the HPN patches. It's become too cumbersome to
maintain these patches as demonstrated by the fact that we haven't
updated OpenSSH in quite some time. If people want additional
functionality in their OpenSSH, it's available in dports
(security/openssh).

Instead of just silently ignoring removed options in people's
configurations, I decided to treat these as errors so that the admin
will need to decide to remove it from their configuration or install the
dport to get the functionality back.