Convert a few ownership comments with std::unique_ptr.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@215853 91177308-0d34-0410-b5e6-96231b3b80d8
Update for llvm api changes.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@215856 91177308-0d34-0410-b5e6-96231b3b80d8