Upgrade OpenSSH to 7.3p1.

This is the last version of OpenSSH which does not break compatibility
more than we can live with in a stable branch. Further commits will
follow to backport some bug fixes from newer versions.

The sshd breakage in the previous attempt was due to an upstream bug
(a 0 was changed to a 1 while refactoring send_rexec_state() in sshd.c)
which only manifested itself when sshd was built with SSH 1 support.

Approved by: re@

Revert OpenSSH 7.3p1; something went wrong between testing and committing.

Approved by: re@

Upgrade OpenSSH to 7.3p1.

This is the last version of OpenSSH which does not break compatibility
more than we can live with in a stable branch. Further commits will
follow to backport some bug fixes from newer versions.

Approved by: re@

MFH (r296633): upgrade to 7.2p2 (fixes xauth command injection bug)
MFH (r296634): re-add aes-cbc to server-side default cipher list
MFH (r296651, r296657): fix gcc build of pam_ssh

PR: 207679
Security: CVE-2016-3115

MFH (r265214, r294333, r294407, r294467): misc prop fixes
MFH (r285975, r287143): register mergeinfo for security fixes
MFH (r294497, r294498, r295139): internal documentation
MFH (r294328): upgrade to openssh 6.7p1, re-add libwrap
MFH (r294332): upgrade to openssh 6.8p1
MFH (r294367): update pam_ssh for api changes
MFH (r294909): switch usedns back on
MFH (r294336): upgrade to openssh 6.9p1
MFH (r294495): re-enable dsa keys
MFH (r294464): upgrade to openssh 7.0p1
MFH (r294496): upgrade to openssh 7.1p2

Approved by: re (gjb)
Relnotes: yes

MFH (r263712): upgrade openssh to 6.6p1
MFH (r264308): restore p level in debugging output

MFH (r261320): upgrade openssh to 6.5p1
MFH (r261340): enable sandboxing by default

MFH (r257954): upgrade to OpenSSH 6.4p1

Approved by: re (kib)

MFH (r263712): upgrade openssh to 6.6p1
MFH (r264308): restore p level in debugging output

MFH (r261320): upgrade openssh to 6.5p1
MFH (r261340): enable sandboxing by default

MFH (r257954): upgrade to OpenSSH 6.4p1

Approved by: re (kib)