libradius(3): Sync with FreeBSD head.
Here is a summary of the changes.
* Added rad_request_authenticator() which returns the Request-Authenticator
relevant to the most recently received RADIUS response.
* Added rad_server_secret() which returns the Shared Secret relevant to the
most recently received RADIUS response.
* Added rad_demangle() for demangling user-passwords (needed for MS-CHAPv1
MPPE-keys).
* Added rad_demangle_mppe_key() for demangling mppe-keys (needed for
MPPE-keys).
* Added some typecasts for avoiding compiler warnings.
* Fix: better handle wrong usage of the lib (if the programmer has not called
rad_create_request() but rad_put_*(), then a weird error message was
returned).
* Added a new function for putting the Message-Authenticator.
* Verify the Message-Authenticator, if it was found inside a response packet
and silently drop the packet, if the validation failed.
* Implicitly put the Message-Authenticator, if the EAP-Message attribute was
added.
* Added some missing defines.
* Add simple embedded RADIUS server support to libradius, by extending existing
API, keeping backward compatibility.
* Add binding support.
* Alphabetically sort MLINKS in the Makefile.
* Various other bugfixes.
Taken-from: FreeBSD (with small adjustments)