Spec update: treat URLs without a special scheme differently

[domenic]

This matches whatwg/url#185.

This one also runs into several failing tests from the new WPT set. I suspect they are spec bugs, but they could be test bugs or spec-translation-into-JS bugs. They are:

1) Web platform tests parsing <sc://ñ> against <about:blank>:

      AssertionError: href
      + expected - actual

      -sc://%C3%B1/
      +sc://%C3%B1

 2) Web platform tests setters host <view-source+http://example.net/path>.host = "example.com\stuff" \ is not a delimiter for non-special schemes, and it’s invalid in a domain:

      AssertionError: 'view-source+http://example.com\\stuff/path' == 'view-source+http://example.net/path'
      + expected - actual

      -view-source+http://example.com\stuff/path
      +view-source+http://example.net/path

  3) Web platform tests setters hostname <view-source+http://example.net/path>.hostname = "example.com\stuff" \ is not a delimiter for non-special schemes, and it’s invalid in a domain:

      AssertionError: 'view-source+http://example.com\\stuff/path' == 'view-source+http://example.net/path'
      + expected - actual

      -view-source+http://example.com\stuff/path
      +view-source+http://example.net/path

/cc @annevk

We should not merge this until the WPT PRs make it into master

[domenic]

Not sure why GitHub isn't reflecting my force-push here... might have to close and open a new PR.