This commit adds support for custom DNS lookup functions in
dgram sockets. This is similar to the existing feature in net
sockets.
Refs: https://github.com/nodejs/node/issues/6189
PR-URL: https://github.com/nodejs/node/pull/14560
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Wyatt Preul <wpreul@gmail.com>
Reviewed-By: Evan Lucas <evanlucas@me.com>
