Revamp build system yet again to move all external libraries to

Revamp build system yet again to move all external libraries to
end of link.    Basic order is:
	$LDFLAGS internal-libs external-libs $LIBS $LTHREAD_LIBS

LTHREAD_LIBS is last as -lpthread (or equiv) must be last on many systems.
LIBS is next to last as some user might have put -lpthread (or equiv)
in $LIBS.