swift234

[stdlib] Prepare array sort for value semantics

Sorting was a bit of a mess; we had sort functions doing in-place
mutation /and/ returing the value, and people were confused by the
asymmetry of Array's sort() method with other higher-level methods.

Fixes <rdar://problem/17185815> sort([]T, f) mutates the original array
<rdar://problem/17225190> The Array.sort() method should return a sorted array

Swift SVN r18922