Pull up following revision(s) (requested by chs in ticket #546):
sys/external/bsd/acpica/dist/namespace/nsinit.c: revision 1.7
revert rev 1.5, which brings back PR 48494.
that earlier revision itself reverted an upstream bugfix,
and that change fixed some systems but broke others
(in particular, it broke my HP Z800 workstation.)
this latest revision brings us back in sync with upstream.
the current upstream (and this latest flip-flop of our copy)
is clearly correct, since it zeros a buffer which is intended
to be used as scratch space for a single acpica operation.
agreed by christos and ryoon back in april 2014.

(snj)