Implement streaming using moz-chunk-arraybuffer

Implements #4739 with `moz-chunk-arraybuffer`. Support of the http://www.w3.org/TR/streams-api/ will be easier to add.

The PDFJS.disableStream option added to disable this functionality. Currently it autodetects presence of moz-chunk-arraybuffer feature, and if enabled turns on the streaming of the PDF (in addition to range requests). The disableAutoFetch is true when streaming in process.
Remove one of the "loading" in "loading loading".