Use scev based code generation for -polly-parallel builder

git-svn-id: https://llvm.org/svn/llvm-project/zorg/trunk@222107 91177308-0d34-0410-b5e6-96231b3b80d8
Set status of -polly-codegen-scev explicitly

This is in preparation of switching polly by default to SCEV based code
generation.

git-svn-id: https://llvm.org/svn/llvm-project/zorg/trunk@222108 91177308-0d34-0410-b5e6-96231b3b80d8