The ldconfig (8) man-page dates "6 January 1997". There is a later version on tsx-11.mit.edu. This one mentions the possibilty to specify a library type in ld.so.conf
assigned to teg
This is in the ld.so package - redirected.
assigned to jakub
We've included a shiny new ldconfig manpage into man-pages-1.32, which describes the rewritten ldconfig in glibc 2.2.