Added radius_vpt_get_vp() function

which gets a VP from a vpt
Better errors for LHS is regex
Create list references, too
Don't consume input string if it's an unknown list
Don't allow list references in conditions
Added paircmp_op function

Which is taken out of paircmp().  This is pretty much the same,
except it doesn't do regexes, and it gets passed an explicit OP
Add -D dictionary_dir

so that we can load dictionaries before the config files.
Which allows us to parse if/elsif conditions correctly

And ensure we load dictionaries before the config files
Do more sanity checks at parse time on conditions

We can't check "foo" against an attr (but we can do attr == foo)
we can't check attrs of different data types
Switch to new conditional evaluation engine.

Completely re-written.  Smaller, faster, better errors,
and does more.