Fix section links in the conformance section

The problem was a typo: parser instead of parsing. Also link to the
sections instead of the headings, which should stay the same even if the
nesting changes.
Use https:// for spec.whatwg.org (http:// redirects)
Use https:// for www.w3.org/Bugs/Public (http:// redirects)
Update CSS spec references (css3-* redirects to css-*)

The titles and editors have also changed, so update that as well.
Update DOM reference

E.g. https://encoding.spec.whatwg.org calls it just "DOM".
Change IndexSizeError reference from DOM to Web IDL
Add www to google.com (it redirects)
Sync with "entry script" changes in HTML

The terminology changed in August 2013:
https://www.w3.org/Bugs/Public/show_bug.cgi?id=18242
https://www.w3.org/Bugs/Public/show_bug.cgi?id=22863
Be consistent with Tab Atkins Jr.

http://krijnhoetmer.nl/irc-logs/whatwg/20141018#l-417
Merge pull request #157 from foolip/link-checker

Fix link and reference issues found by http://validator.w3.org/checklink
Mark the Media Accessibility User Requirements reference non-normative

The start of the references sections says:
All references are normative unless marked "Non-normative".
Merge pull request #159 from foolip/non-normative

Mark the Media Accessibility User Requirements reference non-normative