Don't warn on NewCallback argument comments, as they are arguments for the
function the callback points to.

Reviewers: djasper

Reviewed By: djasper

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D4722

git-svn-id: https://llvm.org/svn/llvm-project/clang-tools-extra/trunk@214307 91177308-0d34-0410-b5e6-96231b3b80d8