imenu does not index delegates

[josteink]

Obvious omission is obvious. Let's get that fixed.

Rules for indexing:

• do NOT assume nested delegate types (this imenu implementation does not do nested stuff)
• do NOT index delegates as container types (do like enums instead)
• do NOT require access-modifiers, since signature should be easy enough to filter based on the delegate keyword.
• otherwise do just like methods enums (we want these listed as separate types).

[josteink]

The code so far lacks tests, but has shown an error in the code (which also applies to enums): Basically namespaces does not get applied to the type-name.

That could be registered as its own bug, but lets not go completely overboard with issues here :)