Change the semantics of is*Parallel

  The functions isParallel, isInnermostParallel and IsOutermostParallel in
  IslAstInfo will now return true even in the presence of broken reductions.
  To compensate for this change the negated result of isReductionParallel can
  be used.


git-svn-id: https://llvm.org/svn/llvm-project/polly/trunk@214488 91177308-0d34-0410-b5e6-96231b3b80d8