Fix aliases on functions in collections.

[dburgener]

No description provided.

[dburgener]

This is a partial fix for #194. It addresses the case of an @alias on a function inside a collection.

It doesn't address two other issues:

1. Aliasing the collection itself
2. The error reporting if a function isn't found claims the collection doesn't exist, when in fact it's the function in the collection that doesn't exist.

Those are obviously important, but in my opinion, the issue here is the most important, and also it's the easiest of the three to fix. The above two probably require collection information to be better propagated through the code. I'd like to merge this fix and then rewrite #194 to refer specifically to collection propagation.