Make TOC hideable

Currently, if an extension doesn't want a TOC, it has to remove it manually.
This change wraps the TOC in markers that make it easy to remove it in ParserOutput
on demand without fragmenting the parser cache with stuff like "use/not use TOC".

Change-Id: I2889bcb9eb999c9049601e92440132118e1a8a41
Merge "Make TOC hideable"