python interface: properly handle isl_bool return type
python interface: properly handle isl_bool return type

In particular, the corresponding python wrapper should raise
an error on a negative result and return True or False
(rather than 1 or 0) otherwise.

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

tobig/isl,UBERTC/isl,nicolasvasilache/isl,BenzoSM/isl,nicolasvasilache/isl,PollyLabs/isl,tobig/isl,PollyLabs/isl,BenzoSM/isl,BenzoSM/isl,UBERTC/isl,inducer/isl-mirror,UBERTC/isl,nicolasvasilache/isl,Meinersbur/isl,PollyLabs/isl,nicolasvasilache/isl,BenzoSM/isl,Distrotech/isl,Distrotech/isl,PollyLabs/isl,Distrotech/isl,inducer/isl-mirror,nicolasvasilache/isl,UBERTC/isl,inducer/isl-mirror,Meinersbur/isl,PollyLabs/isl,Meinersbur/isl,Distrotech/isl,Distrotech/isl,inducer/isl-mirror,tobig/isl,inducer/isl-mirror,Meinersbur/isl,tobig/isl,BenzoSM/isl