I just checked in nettle.pc.in and hogweed.pc.in. configure then generates nettle.pc and hogweed.pc, for use wiith pkg-config.
I don't have any previous experience with pkg-config, so comments are much appreciated.
Not yet any make rules to install them. I don't know if installation should be unconditional, or if one should first check, somehow, if pkg-config is installed. (And then hogweed.pc should be installed only if the hogweed library is built and installed).
Apparantly, at least one user wants pkg-config support, see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=634294
Regards, /Niels