Change do-while to repeat-while.

Change all uses of "do { ... } while <cond>" to use "repeat" instead.
Rename DoWhileStmt to RepeatWhileStmt. Add diagnostic suggesting change
of 'do' to 'repeat' if a condition is found afterwards.

<rdar://problem/20336424> rename do/while loops to repeat/while & introduce "repeat <count> {}" loops

Swift SVN r27650

stdlib/public/core/SwiftNativeNSArray.swift

@@ -165,7 +165,7 @@ extension _SwiftNativeNSArrayWithContiguousStorage: _NSArrayCoreType {
   internal override func withUnsafeBufferOfObjects<R>(
     @noescape body: UnsafeBufferPointer<AnyObject> -> R
   ) -> R {
-    do {
+    repeat {
       var buffer: UnsafeBufferPointer<AnyObject>
       
       // If we've already got a buffer of bridged objects, just use it