Attaching comments to declarations: find comment attached to any redeclaration

Not only look for the comment near the declaration itself, but also walk the
redeclaration chain: the previous declaration might have had a documentation
comment.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@161722 91177308-0d34-0410-b5e6-96231b3b80d8
7 files changed