ChangeLog rotation

[Tom Tromey]

I'd like to put most of ChangeLog into a new file, ChangeLog-2003 (or
maybe a couple new files depending on size).  At the same time I'd
like to rename testsuite/ChangeLog and instead have test suite changes
show up in our top-level ChangeLog -- I think this is clearer, it
keeps test suite changes next to their fixes, and I wish we had done
it since day 1..  Finally in the future I think we should just make a
new ChangeLog each Jan 1.

Any objections?  I'll do this on Friday unless there's arguments
against.

Tom