cvsps: add two more tiebreakers in cscmp
test-convert-cvs.t has been a little flaky for a while now. Add an
extra tiebreaker in cscmp so that all the cases in the test will sort
reliably.
Without this patch, test-convert-cvs.t failed after 346 runs. With
this patch, I stopped trying to get it to fail after 615 runs. While
not conclusive, that makes me pretty optimistic that this is a working
fix.