Begin to replace all of fs.js with node.js original source.

Instead of implementing our own, we simply implement the 'fs' bindings
interface that node.js sources expect. This is an interim commit with
some failing tests. Currently all of fsStatSpec.js passes. All but 3
tests in fsSpec.js pass, and there are still some issues with
fsStreamSpec.js.
Allow non-numeric properties to be set upon the backing-object for buffer.
Debug stuffs
Remove unnecessary debug output. Don't assume this.pos is updated in C++

In the node fs.js sources, it appears that some values are passed by
reference and the side effects on these values in C++ land seem to be
assumed in places. I hope this is a correct assumption and not just a
stab in the dark.
Adjust fs stream specs
If position is undefined, use posix.read().  If position is defined, use posix.pread().
Get all of fs.ReadStream specs passing.
Complete implementation of fs bindings.

Still a couple of odd test failures, but working well overall.
Fix failing fsStreamSpec tests