node.js backend resurrected

[Anil Madhavapeddy <anil@xxxxxxxxxx>]

I've refreshed Thomas' node.js backend for Mirage to the latest ocamlbuild 
framework, and it works for very basic stuff such as the thread sleeping test 
in tests/basic/sleep, when compiled with mir-node and run with "node 
_build/sleep.js" (see below).

Next step: will take a look at re-binding the OS.Netif (via the pcap interface 
in Node) and seeing how well the TCP stack performs when compiled under 
Javascript.  If anyone's interested in playing with the JS backend, let me know.

-anil

click:sleep avsm$ node _build/sleep.js 
31 Jul 23:27:56 - start: four
31 Jul 23:27:56 - 

31 Jul 23:27:56 - iteration: four 1
31 Jul 23:27:56 - 

31 Jul 23:27:56 - start: three
31 Jul 23:27:56 - 

31 Jul 23:27:56 - iteration: three 1
31 Jul 23:27:56 - 

31 Jul 23:27:56 - start: two
31 Jul 23:27:56 - 

31 Jul 23:27:56 - iteration: two 1
31 Jul 23:27:56 -