Previously we stripped attribute prefixes, reading
`xml:lang` as `lang` for example. This resulted in
two duplicate `lang` attributes when `xml:lang` and
`lang` were both used. This commit causes the prefixes
to be retained, and also avoids invald duplicate
attributes.
Closes#6938.
- With epub extensions, check for epub:type in addition to type.
- Fix problem with noteref parsing which caused block-level
content to be eaten with the noteref.
- Rename pAnyTag to pAny.
- Refactor note resolution.
