Missing case for NE operator in BoxRegion.cmpOp. This affects the check routines
for the != operator in the parametric/exact engines, e.g., for state formulas
such as s!=t
git-svn-id: https://www.prismmodelchecker.org/svn/prism/prism/trunk@11976 bbc10eb1-c90d-0410-af57-cb519fbb1720