Init, Mainloop and Shutdown implemented. Doesn't quite work yet though...
First somewhat working version. At this time requires a tweak to nacl_io/socket/udp_node.cc where SentTo() is handed PP_BlockUntilComplete(), and non-negative return values are treated as a success. This likely diminishes performance but is needed until https://code.google.com/p/chromium/issues/detail?id=154338 has been fixed. Needs more testing!