Previously we would fail in some parts of the code if we did not have a
premade configuration, now we use any code that was marked as Linux, BSD and
Solaris as our basis in order to support building unknown Unix systems.
These are just minor tweaks to make sure the 'make install' part does
what it is supposed to do. I also removed some commented code in the
dtmail Makefile related to SunOS, as that is not currently suppoerted
anyway.
Also, restructure some of the dependencies in the lib/tt binaries. We
will link with libtt (which will include libtirpc as a dependency),
and XTOOLLIB - all the right X11 stuff without needing to add it to
every OS. Removed several uneeded OS specializations ("if LINUX",
etc) as a result.