[monit] RADIUS support in Monit

[Alan DeKok]

  There have been a few calls on the FreeRADIUS list for RADIUS support
in Monit.  I've taken a bit of time, and added a basic skeleton of the work:

http://savannah.nongnu.org/bugs/index.php?27403

  It's copied from the other templates, and modified to do RADIUS.

  As background, RADIUS is a UDP protocol with certain packet format and
authentication requirements.  The issue is to get the correctly
formatted packet from Monit to the RADIUS server, with the correct
signature.

  The code looks like it does that, but I haven't had a chance to test
it.  The basic plumbing seems OK: it's patched into Monit in the same
way that everything else is.

  I still need to test the packet send/receive functionality.

  The only real question is how to give a "shared secret" from the monit
configuration to the check_radius() routine.  RADIUS needs this for
packet signing, and it can be different for every RADIUS server.

  For now, I've hard-coded it.  It would be good for someone who knows
more than I do about Monit to add some minor configurability.

  Alan DeKok.