Remove generated code

It looks like at some time in the past, markup generated by respec was committed as source. Or maybe these are artifacts from before this document used respec.

This will be hard to review, but these are the changes:
* dfn tags don't need an id attribute
* a tags to internal references only need a title attribute (and never any others) if the text content does not match the dfn content as might happen with plurals
* rfc2119 keywords need no markup when they're uppercase
Filed issue #52 for this.