heads up: library work requires full rebuilds

[John Marino]

I've already "privatized" three libraries, and there's a fourth in the
works.  Each time I relocate a library, a full build is required.  (this
is to avoid ambiguity with similar dports libraries)

After a bulk build check, we plan to relocate the libraries again to
utilize rpath and move them out the standard library search path.  I'm
being careful but consider the head potentially unstable for a few days.
 If this is scary, you want want to hold off updating for a week or so.

Thanks,
John