Enable quantifier unfolding by default
Until #3703 is resolved, quantifications over subsets are only
evaluated correctly if they are unfolded, i.e. explicitly
qtfer.setUnfold(true)
is invoked.
To implement a more defensive strategy, the default value of
IQuantifierExpression::unfold
should be set to true
and all explicit
invocations of setUnfold()
in the code should be removed.
(from redmine: issue id 3787, created on 2019-07-30)