swift234

[stdlib] Pattern match Ranges efficiently again.

Fixes <rdar://21091371>.  When SequenceType acquired a O(N) 'contains'
method, the code for pattern matching a Range started using that method
instead of implicitly deducing a HalfOpenInterval.

We still have a problem though:

  (1_000_000..<1_000_000_000).contains(1)

will compile and appear to hang at runtime.  I'll bring this up on the
mailing list.

Swift SVN r28998