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.
Some files were trying to access the global includes directy in the
build area with things like #include <api/c/tt_c.h>, which is now
wrong. Se we fix all of those up. tt_c.h and tttk.h are now global,
so we no longer need to root around various build dirs to find them.
TT builds again.
