[whatwg] 'Applicable Specifications'' Relevance Authors

[Smylers]

The definition of an 'applicable specification' is marked as only having
relevance for implementations:
http://www.whatwg.org/html#other-applicable-specifications

I think that the paragraph which defines an applicable specification and
the note that follows it are relevant to authors, too -- in particular
authors wondering if they can extend HTML.

Currently 'HTML5 for Web Developers' has a link 'other applicable
specifications' which doesn't go anywhere:
http://developers.whatwg.org/elements.html

Cheers

Smylers