[bugfix] Moved `INSPECT_MAX_BYTES` to the buffer module.

There's a mistake in pull request #2154 concerning `INSPECT_MAX_BYTES`

From the [docs](http://nodejs.org/api/buffer.html#buffer_buffer_inspect_max_bytes):

"Note that this is a property on the buffer module returned by `require('buffer')`, not on the Buffer global, or a buffer instance."

A short test showed that, despite the ambiguity (right? :) of the sentence, `INSPECT_MAX_BYTES` does neither exist on the Buffer global nor on a buffer instance.