test-convert-cvsnt-mergepoints: ignore differences between CVS 1.11 and 1.12.
- factor out cvsci function (similar to other test-convert-cvs* scripts)
- add filterpath function (also similar to other scripts)
- generally munge the output of CVS
- add lots of output to make it easier to follow when things go wrong
This doesn't make the test pass reliably under CVS 1.11; it just makes
it behave the same as under CVS 1.12, i.e. sometimes it passes and
sometimes it fails. Failure is more frequent with faster hardware.