Transforms: Introduce Transforms/Utils.h rather than spreading the declarations amongst Scalar.h and IPO.h

Fixes layering - Transforms/Utils shouldn't depend on including a Scalar
or IPO header, because Scalar and IPO depend on Utils.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@328717 91177308-0d34-0410-b5e6-96231b3b80d8
42 files changed