module: remove unnecessary property and method

`require.paths` property and `require.registerExtension` function have
been throwing errors when used. They both are like this for years now.
This patch removes them from the system.

PR-URL: https://github.com/nodejs/node/pull/2922


Reviewed-By: Roman Reiss <me@silverwind.io>
Reviewed-By: Brian White <mscdex@mscdex.net>
Reviewed-By: Сковорода Никита Андреевич <chalkerx@gmail.com>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>