This corresponds with the editorial change to the HTML standard
introducing the parsing mode enum of:
01c45cede
And a follow up normative change of:
508706c80
Making fragment parsing derive its scripting mode from the context
document.
For XHTML documents, resolve named character entities (e.g., )
using the HTML entity table via a getEntity SAX callback. This avoids
parsing a large embedded DTD on every document and matches the approach
used by Blink and WebKit.
This also removes the now-unused DTD infrastructure:
- Remove resolve_external_resource callback from Parser::Options
- Remove resolve_xml_resource() function and its ~60KB embedded DTD
- Remove all call sites passing the unused callback
