Exporting imported names

[jonmeow]

In order to support exporting imported names, add export import library <library> and export <name reference> syntax.

[jonmeow]

Note, not sure what the best way is to see if people agree on the syntax choice -- I was thinking if there's a preference for an alternative, I can adjust the proposal. But export import at least sounded like people though it'd be okay, in the discussion.

[jonmeow]

@zygoloid FYI I want to be sure you notice the namespace commit. I don't think it really changes the proposal, but it I was trying to close some design gaps I realized existed (naively, export NS; would only export the namespace itself, not contents). [also, export OtherPackage.Name; wasn't explicitly disallowed, and is now]

[zygoloid]

Still LG with namespace changes. I agree that disallowing namespace exports for now is the right choice, consistent with the existing rule that namespaces are exported iff they contain anything exported.

[chandlerc]

And merging (confirmed with the author).