(Bug 50944) Fix stale regexp in wikitext escaping for ext tags

* The regexp that tested for extensions in wikitext escaping hadn't
  been updated to reflect changes to typeof added in the tokenizer.

* Added new test.

* Nested ref tests now fails in several modes because the inner
  ref will now get nowiki escaped whereas it is not strictly necessary
  since a nested <ref> is a special case that Parsoid can handle by 
  emitting as plain text.

  But, the wikitext escaping code doesn't have that knowledge.
  For now, just updating the blacklist, but this can be fixed
  if deemed important enough.

Change-Id: I816ae2d5e3423c830692fe111f36b744ee1d4238
Merge "(Bug 50944) Fix stale regexp in wikitext escaping for ext tags"