Highlight by name parameters at call site (#1000989)

Note that to decide if CallByNameParameter is merely defined or actually called, we cannot rely on the Symbol alone. To deal with this, handleCallByNameParamSpecialCase(...) also considers the associated tree.

I don't know if this is the kind of implementation you had in mind, but it seems to work at far as I can tell. Please tell me what you think.
This smells...