don't add Reviewed-by footers for self-approvals

Yes, for master and any stable branch we should always have a reviewer for our code. But it might be that we have experimental or some kind of work in progress (wip) branches in which a more relaxed reviewing mechanism would still be acceptable. For instance, in Qt Creator we currently have a branch under the name wip/clang with very few people working on it. In such cases, when it happens that the author reviews his/her own change, I'm not sure if it makes sense to append the Reviewed-by to the log with the same name.

Perhaps it would be possible to check if the names match and if there's only one reviewer, replace it to something like "Reviewed-by: TrustMe" or just leave it empty. If there are other reviewers, the matching one could simply be dropped.