add internal references to protocol spec
the HTML protocol spec would be easier to refer people to if it had internal references for the relevant bits.
Attached are 5 patches to the spec that
- make the document valid XHTML 1.0 Transitional (which it claims to be)
- add internal references to relevant sections
- provide styling so that the targeted section gets a highlight
- provide some internal and external links for easier navigation for readers
(from redmine: created on 2015-05-22)