Compatibility changes for Angstrom (Node 0.8)

Angstrom for Beaglebone Black is still at version 0.8.22 of node.js.  I
had to make a few changes to build node-pru.  These follow the
guidelines from
https://github.com/joyent/node/wiki/Api-changes-between-v0.8-and-v0.10 .

- add explicit cast to (uv_after_work_cb) to 4th arg of call to
uv_queue_work
- use backwards-compatible version of Init, that doesn't receive a
handle to module