(Bug 70894) Fix regressions introduced by 6e302233 (found in RT-testing)

* While testing for 'simple-link' serialization, normalize "_" chars
  in both content-string and link-target strings.
* Fixes regressions found in testing.
* No changes to parser test results (TODO: Add new tests).

Change-Id: I172cb0c7fb86e7271a25d3d2043b31dfa23891ee
Merge "(Bug 70894) Fix regressions introduced by 6e302233 (found in RT-testing)"