deps: make node-gyp work again on windows

* Fetch from the correct url.
* Link compiled addons with iojs.lib instead of node.lib.
* Disable checksum checks for iojs.lib until our website supports
  them.

PR: https://github.com/iojs/io.js/pull/422


Reviewed-by: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-by: Rod Vagg <rod@vagg.org>