(Bug 58469) Fix broken urlparsing in wikitext escaping

* Wikitext escaping relied on verifying whether an extlink url
  was valid by tokenizing it. However, the url checking code was
  subtly broken. This used to work at one point when url parsing
  didn't use env, but broken when url checking uses env. We broke
  this because of lack of tests.

  Fixed this by passing in args array into the tokenizer always.
  The interesting thing is that a crasher in Util.isProtocolValid
  gets suppressed somewhere (probably the peg-tokenizer?).

* In addition, suppressed RFC/PMID/ISBN escaping when those strings
  are present in link content since those will not get parsed as
  RFC/PMID/ISBN links in that context.

* Added parser tests.

Change-Id: Ie37e120384323010638915fb7a385df7377bbbc5