This decreases total testing time by over a minute on my old Mac Pro.
It probably has much less effect on systems with fewer cores, but shouldn't
be any worse there.
Swift SVN r22745
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
