isl_basic_map_preimage_multi_aff: call isl_basic_map_* functions on basic map
isl_basic_map_preimage_multi_aff: call isl_basic_map_* functions on basic map

Even though, internally, basic sets and basic maps are the same,
it is better to call the correct functions.  This was
broken in 156e2db (generalize isl_basic_set_preimage_multi_aff to
isl_basic_map_preimage_multi_aff, Fri Apr 12 17:26:10 2013 +0200).

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

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