Move the call to nnf inside skolemize up to where skolemized is called inside nnf.
Move ['lit l] up into the last pattern in proveo
This is a broken WIP of a translation of nnf into a logic program.

The only known defect is that the binder that is created for
universally quantified formula is reified on output, which won't unify
with the binder in proveo.
Fix broken universally quantified formula. Call nnfo from find-proof.
whitespace cleanup
remove comments
whitespace cleanup'
whitespace
drop 'lit tag
Modify nnfo to put less branching forumula on the left
first attempt at fixing substitution bugs in nnf (still broken)
fix bug/typo in proveo, introduced when 'lit was dropped
Replace relational attempt with working ->nnf
extract spread-juncts from ->nnf*
Explode ->nnf* into smaller reusable functions. Remove CNF code.
remove sym tag
Update test-proveo-1
Rename tag to tag-lits. Change a simple cond to if.
Remove spurious doall expressions.
whitespace cleanup