Human-readable section ID support
It adds the ability to replace the current section ID escaping
schema (.C0.DE) with a HTML5-compliant escaping schema that is
displayed as Unicode in many modern browsers.
See the linked bug for discussion of various options that were
considered before the implementation. A few remarks:
- Because Sanitizer::escapeId() is used in a bunch of places without escaping, I'm deprecating it without altering its behavior.
- The bug described in comments for Parser::guessLegacySectionNameFromWikiText() is still there in some Edge versions that display mojibake.