isl_basic_map_union: add memory management annotation
isl_basic_map_union: add memory management annotation

Signed-off-by: Sven Verdoolaege <e5350bbed4977f5eb8ae1dc6abd9ae59d21ace75@kotnet.org>

Meinersbur/isl,tobig/isl,nicolasvasilache/isl,PollyLabs/isl,inducer/isl-mirror,nicolasvasilache/isl,inducer/isl-mirror,Meinersbur/isl,inducer/isl-mirror,PollyLabs/isl,PollyLabs/isl,Meinersbur/isl,nicolasvasilache/isl,inducer/isl-mirror,PollyLabs/isl,Meinersbur/isl,PollyLabs/isl,tobig/isl,tobig/isl,nicolasvasilache/isl,nicolasvasilache/isl,tobig/isl,inducer/isl-mirror