SourceKit editor.open request doesn't return global declarations or enum cases

[beltex]

Currently, enum cases (not the enum itself) are only shown if documented individually. However, enum cases are often self-explanatory and wouldn't have any documentation (units, currency, etc.). Thus, I think it be handy to have all cases shown in the enum declaration by default (or at least in the See more link).

[jpsim]

This is a bug in SourceKit on Apple's side, unfortunately. See rdar://18845613.

We could add a workaround to sourcekitten by making cursorinfo requests for offsets at case * when an source.lang.swift.decl.enum is detected. Only searching for case * inside the enum body based on its bodyoffset and bodylength.

[beltex]

Darn, thanks @jpsim!

[jpsim]

Closing as dupe of #74.