Add Parsoid-specific tests for link trail and -prefix escaping

This is intended to test the escaping code developed in I627dd609d4eb0. The
link prefix code does not pass yet, possibly because of some bug in
language-specific tests or our local islandic language config.

Change-Id: I53289110e3f9e4f840b2f45594e819c9655a17b4
Merge "Add Parsoid-specific tests for link trail and -prefix escaping"