Push the raw_ostream through the template diffing code.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@175896 91177308-0d34-0410-b5e6-96231b3b80d8
Use raw_ostream::indent, update comment.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@175897 91177308-0d34-0410-b5e6-96231b3b80d8