- Buffer.toString('ascii', 0, 0) incorrectly returns the entire contents
  of the buffer. Fix this.
- Provide similar behavior to Buffer.write() and Buffer.copy() when
  dealing with 0-length in valid and invalid byte ranges.

This way, require("/foo") will work if there is a "foo.js", or a file named
simply "foo" with no extension.

Callbacks should always be the last argument.

This is ever so slightly less efficient than caching based on ID, since the
filename has to be looked up before we can check the cache.  However, it's
the most minimal approach possible to get this change in place.  Since
require() is a blocking startup-time operation anyway, a bit of slowness is
not a huge problem.

A test involving require.paths modification and absolute loading. Here's the
gist of it.

Files: /p1/foo.js /p2/foo.js

  1. Add "/p1" to require.paths.
  2. foo1 = require("foo")
  3. assert foo1 === require("/p1/foo") (fail)
  4. Remove /p1 from require.paths.
  5. Add /p2 to require.paths.
  6. foo2 = require("foo")
  7. assert foo1 !== foo2 (fail)
  8. assert foo2 === require("/p2/foo") (fail)

It's an edge case, but it affects how dependencies are mapped by npm.
If your module requires foo-1.2.3, and my module requires foo-2.3.4,
then you should expect to have require("foo") give you foo-1.2.3, and
I should expect require("foo") to give me foo-2.3.4.  However, with
module ID based caching, if your code loads *first*, then your "foo"
is THE "foo", so I'll get your version instead of mine.

It hasn't yet been a problem, but only because there are so few
modules, and everyone pretty much uses the latest version all the
time.  But as things start to get to the 1.x and 2.x versions, it'll
be an issue, I'm sure.  Dependency hell isn't fun, so this is a way to
avoid it before it strikes.

The tests did not accurately test for a strict equality, meaning that the
number == to the string.

* handles NaN and Infinity
* works with arrays from other contexts

Now that process.version doesn't say if the build is debug or not.

The V8 upgrade changed the stacktrace reports (?)