Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Pull in OpenSSH 6.2p2 from head.

Upgrade to OpenSSH 6.2p1. The most important new features are support
for a key revocation list and more fine-grained authentication control.

Vendor import of OpenSSH 6.2p1.