ScopInfo: Allow simple 'AddRec * Parameter' products in delinearization

We also allow such products for cases where 'Parameter' is loaded within the
scop, but where we can dynamically verify that the value of 'Parameter' remains
unchanged during the execution of the scop.

This change relies on Polly's new RequiredILS tracking infrastructure recently
contributed by Johannes.

llvm-svn: 250019