More future plans.
Replaced the horribly memory-inefficient NSIndexSet operation to get the list of selected indices in the Mac OS X Listbox with a far simpler option that avoids deferring some of the work (apart from objc_msgSend() calls) to cgo and the use of reflect.SliceHeader at all! It just grabs the indices from the NSIndexSet one at a time using the previous index as an anchor.