This patch changes config/cf/darwin.cf and adds config/
cf/darwinLib.(rules|tmpl) to build shared X client
libraries. Apply it with patch -p1 <shlib.patch in the
xc directory. I have verified that bootstrapping on a
clean system works, that the correct paths are coded
into the libraries and that the programs build are
linked against these shared libraries.
Someone should check if this also builds correctly on
pure Darwin (although I'm quite sure it will).