Fix OpenSSH multiple vulnerabilities by backporting three changes
from OpenSSH-portable master.

Git revisions: 45b0eb752c94954a6de046bfaaf129e518ad4b5b

		5e75f5198769056089fb06c4d738ab0e5abc66f7
		d4697fe9a28dab7255c60433e4dd23cf7fce8a8b

Reviewed by: des
Security: FreeBSD-SA-15:22.openssh