Update the embedded PDF.js code to v1.0.712

This PR depends on https://github.com/hypothesis/h/pull/1593; please merge that first.

   * * *

These files come straight from the generic build of PDF.js v1.0.712.

There are only two changes:

 - I did not include the 1M test pdf document
   (See 8c20039 )

 - I have kept our 1-line code insertation in viewer.html.
   (See da34694 )