fs: validate args of truncate functions in js

This patch

 1. moves the basic validation of arguments to `truncate` family
    of functions to the JavaScript layer from the C++ layer.

 2. makes sure that the File Descriptors are validated strictly.

PR-URL: https://github.com/nodejs/node/pull/2498


Reviewed-By: Trevor Norris <trev.norris@gmail.com>