Move libfmt, libutf into subdirectories of lib9.
Add poll-based socket i/o to libthread, so that we can
avoid using multiple procs when possible, thus removing
dependence on crappy pthreads implementations.
Convert samterm, acme to the single-proc libthread.
Bring libcomplete, acme up-to-date w.r.t. Plan 9 distribution.
which were completely bogus. (Libthread used to ignore them but
not anymore. Maybe we really should ignore them, but that breaks
Venti, which needs *really* big stacks.)
