isl_basic_map_drop_redundant_divs_ineq: extract out drop_div_and_try_again
isl_basic_map_drop_redundant_divs_ineq: extract out drop_div_and_try_again

This simplifies the code of isl_basic_map_drop_redundant_divs_ineq a bit.

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

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