Update contentOffsets for extlinks in shiftTokenTSR

* This should bring contentOffsets to absolute page offsets
  rather than being relative to the chunk that was tokenized.

* This should eliminate a lot of the DSR mismatch warnings and
  possibly some errors.

  One selser test had its blacklisted output change, and the
  new result is more accurate than the previous one.

Change-Id: I9839c1cce4469ff45a88a683deec296c6c73f9ea