interval->day patch and docs

Thanks, Bruce, for improving and applying the interval->day patch.
I've been busy with work and slow in catching up on what you actually
did (I still need to go back and look) and look forward to learning
what remained to make the patch more complete.

I'm hoping to get the docs and some additional regression tests
finished this weekend. It looks like there may be a problem with the
patch on a couple of platforms (AIX 5.2, kookaburra on the build-
farm; recent report on -hackers from Oliver Prenant, "regressin
failure on latest CVS") and hope to do what I can (if anything) to
fix it.

Thanks again!

Michael Glaesemann
grzm myrealbox com