Force token category for unknown identifiers that are logically parameter names in type definitions

[pgoodman]

Here, the parameter names, e.g. write, offset, etc. end up being basically unparsed junk in the type, not associated with anything in particular. It would be nice to special case a token category for these.

[pgoodman]

This can't purely be solved in the API, or not without some ugliness of having the API inspect the token contexts, so I've added some of that logic into the indexer. But the logic is incomplete, due to inconsistencies between how parameters sometimes link to the function prototype, or to one of the parameter types.

[pgoodman]

Still happening: