linking against installed libraries or finding installed headers except
for those that are explicitly linked into ${BUILDLINK_INCDIR} and
${BUILDLINK_LIBDIR}.
* Don't prototype history functions directly, but use
<readline/history.h> to pull them in. This allows us to use libedit's
readline emulation.
* Add INSTALL/DEINSTALL scripts to handle coda-server and coda-client both
installing coda-setup-ports and codaconfedit.
* Try to remove ${PREFIX}/etc/coda at post-deinstall time.
