isl_coalesce.c: is_adj_eq_extension: extract out extend
isl_coalesce.c: is_adj_eq_extension: extract out extend

This will make it easier to extend the remainder of is_adj_eq_extension
in a subsequent commit.

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

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