swift234

Avoid unnecessary calls to CodeCompletionString::getName during sorting

This improves run time of this particular function by up to 8x in my
testing. For *really* large sets of code completions (I tested top-level
completion with Cocoa imported) this gives a 30-40% improvement across
the request, not including time spent in the client.  The tradeoff is a
slight increase in peak memory usage (I saw 0.7% or 1.2 MB for the
top-level Cocoa case).

<rdar://problem/20355626>

Swift SVN r26748