Introduce -polly-canonicalize pass

This ModulePass schedules the set of Polly canonicalization passes. It is a
debugging tool that can be used to preoptimize .ll files for Polly processing.

git-svn-id: https://llvm.org/svn/llvm-project/polly/trunk@198376 91177308-0d34-0410-b5e6-96231b3b80d8