streamline isl_pw_qpolynomial_bound tests
streamline isl_pw_qpolynomial_bound tests

This will make it easier to add more tests in the next commits.

Signed-off-by: Sven Verdoolaege <235c10dd23b819f81cdc9756a251746bc184cab6@gmail.com>

Meinersbur/isl,Meinersbur/isl,Meinersbur/isl,Meinersbur/isl