Forum OpenACS Q&A: Response to ACS/pg is disrupting AOLserver
Also, I've taken a closer look at postgres.c. It declares the class at the top. It uses Ns_DbAddColumnInfo in Ns_PgGetTableInfo. Finally, it defines the class lower. That's all there is to the c side of things.
It sounds, however, that there's something else to the makefile that I don't know about.