Vendor import of OpenSSH 6.3p1
Ditch the random seeding code, which never really worked as intended.
Add config variables to enable / disable individual host key algorithms.
Clean up the host key generation code.

Approved by:	re (gjb)
MFC after:	3 weeks
Upgrade to 6.3p1.

Approved by:	re (gjb)
Stability fixes for Intel LynxPoint XHCI controllers. Disable XHCI port
routing if we get certain errors. Poll for command completion upon
command timeouts. The XHCI error events might not generate interrupts.

MFC after:	1 week
Reported by:	Daniel Gerzo <danger@rulez.sk>, Antonis Anastasiadis <anastasiadis@datalive.gr>
PR:		usb/181159
Approved by:	re (gjb)
Pull in all the OpenSSH bits that we'd previously left out because we
didn't use them.  This will make future merges from the vendor tree much
easier.

Approved by:	re (gjb)