Style the revision notes differently from in-thread comments.

When using the Revision linking syntax (e.g. r12345), the thread is automatically updated with the Revision note entered at check-in.  Since the Revision note and the in-thread comments are all styled the same, it looks like a time warp his happening.  Therefore, it would be more clear that these were two different kinds of information if the Revision notes and the thread comments were not styled the same when they appear on the same page.