[url] Update url-problem-statement.xml (#17)

update a few references and other minor editorial
You can merge this Pull Request by running:

  git pull https://github.com/masinter/url develop

Or you can view, comment on it, or merge it online at:

  https://github.com/webspecs/url/pull/17

-- Commit Summary --

  * Update url-problem-statement.xml

-- File Changes --

    M docs/url-problem-statement.xml (85)

-- Patch Links --

https://github.com/webspecs/url/pull/17.patch
https://github.com/webspecs/url/pull/17.diff

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https://github.com/webspecs/url/pull/17