Add audio, image in presentation contexts to content elements.

[skynavga]

I reviewed all 99 instances of references to the term content element, and all of them should include and not exclude audio and image descendants of body. Furthermore, these elements need to be added to 10.4.4.4 step (1) and 10.2.1 (the list of elements on which @style applies - image was already present, but missing audio).

This is an editorial change to correct an inadvertent omission which is substantially backed up by normative text elsewhere, e.g., both audio and image accept style properties which are applied to them, and, therefore, style resolution must apply (in contradiction to the [filter] step of 10.4.4.4 and the [associate region] procedure (defined in terms of content elements). In addition, presentation processing explicitly applies, e.g., see [presentation related element].

[nigelmegitt]

I am querying whether this is truly editorial - to make the argument clearly I think we need more details about the existing normative text that implies that these changes are not substantive. It's going to be tricky because if there are such parts of the text then these changes apparently fall under the third bullet of class 3 in the Process document's Classes of Change, i.e. they clear up an ambiguity, whose source was the previous inconsistency.

[skynavga]

Taking a conservative position, I am relabeling this as substantive.

[skynavga]

Merged early per WG resolution to move to CR3 CfC.