isl_pw_aff_is_equal: check for NaNs in input
isl_pw_aff_is_equal: check for NaNs in input

If the inputs involve any NaNs, then they cannot be equal to each other
since a NaN is not considered to be equal to anything.
The explicit check is required because map_from_pw_aff (which
internally calls isl_basic_map_from_aff) cannot be called
on an isl_pw_aff that contains NaNs.

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

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