isl_map_is_disjoint: use isl_bool_not
isl_map_is_disjoint: use isl_bool_not

This improves readability.

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

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