Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

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

Add a new hash type. This "NT-hash" is compatible with the password
hashing scheme used in Microsoft's NT machines. IT IS NOT SECURE!
DON'T USE IT! This is for the use of competent sysadmins only!

Submitted by: Michael Bretterklieber