Remember to mark emacs-23 changes that should not be merged

[Glenn Morris]

Please remember to mark emacs-23 changes that should not be merged to
the trunk in the commit message. Anything that matches
bzrmerge-skip-regexp will do. It's very confusing to find identical (or
even worse, not-literally-identical-but-having-the-same-effect) changes
in both branches when trying to merge them.