Tooling around specification XML doesn't support extensions

It seems the various scripts don't support generating prototypes and version notes at least. A consequence of this is that we lose an opportunity to automatically detect inconsistencies in the XML for extensions.

Related to that we should probably use automatically generated prototypes in the extension specification.

Start by locating the scripts that generate specification prototypes and version notes, then inspect how they handle the extension specification XML. Done means extensions are supported by both generators and the generated output can help detect inconsistencies in the XML.

Written by the indexing model from the issue text.