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.
Replace this line with `if (!this.loadedChunks[curChunk]) {`