Move helper classes into anonymous namespaces.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@185262 91177308-0d34-0410-b5e6-96231b3b80d8
LoopVectorizer: Pack MemAccessInfo pairs.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@185263 91177308-0d34-0410-b5e6-96231b3b80d8