src: replace ARRAY_SIZE with typesafe arraysize

To prevent `ARRAY_SIZE(&arg)` (i.e., taking the array size of a pointer)
from happening again.

PR-URL: https://github.com/nodejs/node/pull/5969


Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>