Missing headers to build dl

I have all of ruby 1.8.4 running on my OS 10.2.8 mac - nearly…

When I try running extcon.rb in the ext/dl results in
checking for windows.h… no
checking for dlfcn.h… no
so of course the bundle is never built.

Search high, search low, search other macs, I cannot find the
correct header files (i.e. the windows.h file is not the one found
in XP)

I tried, just for jollies, installing the dl.bundle from a 10.4
machine - but the libraries (not too surprisingly) don’t line up.

Anybody know where I might find these 2 header files?