Properly mark the closure parameter to withUnsafeMutablePointers as being

@NoEscape.  It doesn't escape the parameter, and callers are passing their
@NoEscape values down to it.  This isn't being caught so far due to a bug
in the type checker that is about to be fixed.

Author: lattner

stdlib/public/core/ManagedBuffer.swift

@@ -279,7 +279,7 @@ public struct ManagedBufferPointer<Value, Element> : Equatable {
   /// - Note: These pointers are only valid for the duration of the
   ///   call to `body`.
   public func withUnsafeMutablePointers<R>(
-    _ body: (_: UnsafeMutablePointer<Value>, _: UnsafeMutablePointer<Element>) -> R
+    _ body: @noescape (_: UnsafeMutablePointer<Value>, _: UnsafeMutablePointer<Element>) -> R
   ) -> R {
     let result = body(_valuePointer, _elementPointer)
     _fixLifetime(_nativeBuffer)