ARIA6 and ARIA11: Content updates for HTML5 required

[momdo]

Example1 of ARIA6 and example 1-3 of ARIA11 say "HTML4 or XHTML 1.0 document", where we have HTML5 already. They should be updated.
Using HTML5, we can write these examples more easily and clearly, along with Implicit ARIA semantics. Especially, we should review description section of ARIA11 from the viewpoint of ARIA in HTML spec: we have nav element for the purpose, which should replace the navigation role unless otherwise there is a specific reason to rely on WAI-ARIA.

[jnurthen]

These are aria techniques and apply when you (for some reason) cannot use native semantics. We don't need to go into all the whys each time we recommend something.

[joshueoconnor]

@momdo These techniques are relevant for both HTML5 and older legacy code. I suggest leaving this as is.