buffer: alias toLocaleString to toString

Make Buffer.prototype.toLocaleString an alias of Buffer.prototype.toString
so that the output is actually useful.

Fixes: https://github.com/nodejs/node/issues/8147
PR-URL: https://github.com/nodejs/node/pull/8148


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Trevor Norris <trev.norris@gmail.com>