Two part negation involves both an affix on the verb and
an adverb (hypothesized to be selected as a complement in
these cases, because we can't enforce the presence of
modifiers).

Case 1:
-------
--affix can't show up without adverb
--adverb has no other uses where it can modify verbs

Solution:
 Lexical rule adds affix and additional complement requirement
 for adverb, linking up the adverb's semantics as we do with
 the English rule.

 Adverb's lexical specficiations make its MOD value incompatible
 with modifying verbs through the head-adj rules (maybe just
 the head type, but then what about non-finite verbs?)

Case 2:
-------
--affix can occur with our without adverb

Solution:
  Here we need to avoid dropping in two neg_r_rels, one for
  the rule and one for the adverb.  I think the trick will be
  to keep the solution from Case 1, and add a second rule which
  doesn't affect the COMPS list, but does add the negative semantics.
  Same spelling of the affix, if that's desired.  We'll want to
  make sure that only one of the rules can apply in any given
  parse -- so make use of a feature like [NEG bool], which I 
  think we'll need anyway to keep the rules from iterating.
  (Unless there's languages in which they can???)

