Allow loops in non-affine subregions -- SCoP Modeling

  This will allow the ScopInfo to build the polyhedral representation for
  non-affine regions that contain loops. Such loops are basically not visible
  in the SCoP representation. Accesses that are variant in such loops are
  therefor represented as non-affine accesses.

Differential Revision: http://reviews.llvm.org/D8153

llvm-svn: 234713