Use new RADIUS decoder.

It keys off of attribute data type, instead of using hard-coded
functions and checks.  The "long-extended" attrs aren't there yet.
But WiMAX is there (continued, etc.), and it works.

The end result is ~300 LoC smaller than the previous one.

It still needs checks in dict.c to enforce parent/child
relationships in types.  i.e. "evs" can't be a member of any
other data type, etc.