Improvements:
* Removes an unnecessary variable
* Avoids having two variables with the same name
* Avoids re-declaring an existing parameter
* Removes an unnecessary ternary operator
* Avoid an inline short-circuit expression for greater clarity.

The fact that the mode parameter is optional for fs.open and
fs.openSync was not documented.

Problem: Omitting the mode parameter causes the provided callback
parameter to never fire. This was originally fixed in 6078c37b and
later broken in 5f2e9093.

Solution: Overwriting the value of a parameter also overwrites the
reference in the arguments object. This patch works arround this
fact by not touching the mode parameter until a reference to the
callback has been established.

Should re-enable crankshaft; can build w/ snapshot again.

thanks Toshihiro

Closes GH-653.

This is important so that in the future, this will work:

    $ cd ~/dev/js/some-project
    $ npm install redis
    $ node
    > require.resolve('redis')
    '/Users/isaacs/dev/js/some-project/node_modules/redis/index.js'

This works for both ServerResponse and ClientRequest.
Adds three new methods as a couple properties to to OutgoingMessage objects.
Tests by Charlie Robbins.

Change-Id: Ib6f3829798e8f11dd2b6136e61df254f1564807e

Needs more tests.

Thanks Sitelier. Closes GH-651.

See http://code.google.com/p/v8/issues/detail?id=884

This adds support for a cache object to be passed to the
fs.realpath and fs.realpathSync functions.  The Module loader keeps an
object around which caches the resulting realpaths that it looks up in
the process of loading modules.

This means that (at least as a result of loading modules) the same files
and folders are never lstat()ed more than once.  To reset the cache, set
require("module")._realpathCache to an empty object.  To disable the
caching behavior, set it to null.