From Albert Chin: IBM's AIX C compiler complains about "&buf[sizeof

From Albert Chin: IBM's AIX C compiler complains about "&buf[sizeof
buf]", but doesn't complain about the equivalent "buf + sizeof(buf)".
(C89 allows a pointer into an array to point one element past the end of
the array, so both should, at least as I understand it, be legal, and we
decrement the resulting pointer before we use it, so both should be
safe.)