When a cube is updated, a lemma might loose all of its quantified
variables. In this case, it is effectively quantifier free
and might be a version of an already existing lemma.
For that reason, we convert it to quantifier free lemma when
this happens.
Controlled by fixedpoint.spacer.use_quanti_generalizer
measure cumulative time, number of invocations, and number of failed
SMT calls
Relaxing equality in a pattern: if a variable equals a numeral, relax with GE
pob::get_skolems() returns all skolems that might appear in the pob.
New skolems must be added above the largest index in that map,
even if they are not used in the pob itself.
pattern generalization should be done before the pattern is skolemized and
added into the new cube.
