Consider adding hooks/extension points to native host languages

[joanmarie]

AccName mentions native host language elements and attributes (see, for instance, step 2D in the computation). But it doesn't cover all possible host language name sources, nor does it point to the owning specs (e.g. HTML-AAM, SVG-AAM, etc.) This is a source of confusion.

It would be great if we could point to native host language specs -- and do so in a non-normative fashion, because those host language specs already have a normative dependency on AccName; we don't want the reverse.

[joanmarie]

@zcorpan: Please and thank you when you have time.