isl_map_simplify.c: isl_constraint_index: keep track of total dimension
isl_map_simplify.c: isl_constraint_index: keep track of total dimension

This wil be useful in the next commit.

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

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