test isl_set_preimage_multi_aff instead of isl_basic_set_preimage_multi_aff
test isl_set_preimage_multi_aff instead of isl_basic_set_preimage_multi_aff

Since the inputs are not changed, this tests essentially
the same functionality, but it is easier to convert
to C++ in the next commit because isl_set_preimage_multi_aff
is exported to the bindings.

Signed-off-by: Sven Verdoolaege <235c10dd23b819f81cdc9756a251746bc184cab6@gmail.com>

Meinersbur/isl,Meinersbur/isl,Meinersbur/isl,Meinersbur/isl