Just raise exception naturally.

API change summary:

  * require("/sys.js") becomes require("sys")

  * require("circle.js") becomes require("./circle")

  * process.path.join() becomes require("path").join()

http://groups.google.com/group/nodejs/browse_thread/thread/1034fd2ad2cd93e8

use require("/posix.js") to access them.

This reverts commit 9a70abbf.

promise.cancel() is due to return at some point.

Previously was linking just by doing -lv8 or -ludns which could confuse the
build when a system libv8 or libudns was installed.

Using WAF "staticlib" to compile libev tends to confuse it with a system
version. Thanks to mr.binary42 for helping debug.