David, yes all code changes appear in Postgresql's CVS. If you checkout branch REL7_1_STABLE it has a patch in it now. There wasn't an announcement in the bugs list, but I noticed the change in CVS. I did a little testing and it appears to work well.
Don, The only mention I see of createlang in the documentation is in www/doc/bboard.html. This if for the pltcl search that you created. I don't see any mention for plpgsql. Also, it is not mentioned for either language in the OpenACS installation Guide at https://openacs.org/doc/openacs/install/ (which I found very handy).