add LoopToScev maps

git-svn-id: https://llvm.org/svn/llvm-project/polly/trunk@175295 91177308-0d34-0410-b5e6-96231b3b80d8
use apply and ScevParameterRewriter::rewrite instead of SCEVRewriter

git-svn-id: https://llvm.org/svn/llvm-project/polly/trunk@175296 91177308-0d34-0410-b5e6-96231b3b80d8