[test] Add KVO test. XFAIL it pending the ObjC runtime additions.

Swift SVN r17030

test/stdlib/KVO.swift

@@ -0,0 +1,72 @@
+// RUN: %target-run-simple-swift
+
+// FIXME: rdar://15931346
+// XFAIL: *
+
+import Foundation
+
+struct Guts {
+  var internalValue = 42
+  var value: Int { 
+    get {
+      return internalValue
+    }
+  }
+}
+
+class Target : NSString {
+  // This ObjC-typed property is observed by KVO
+  var objcValue: String
+
+  // This Swift-typed property causes vtable usage on this class.
+  var swiftValue: Guts
+
+  init() {
+    self.swiftValue = Guts()
+    self.objcValue = ""
+    super.init()
+  }
+
+  func print() { 
+    println("swiftValue \(self.swiftValue.value), objcValue \(objcValue)")
+  }
+}
+
+typealias KVOContext = CMutableVoidPointer
+
+class Observer : NSObject {
+  var target: Target?
+
+  init() { target = nil; super.init() }
+
+  func observeTarget(t: Target) 
+  {
+    target = t
+    target!.addObserver(self, forKeyPath:"objcValue", 
+      options:NSKeyValueObservingOptions.New | NSKeyValueObservingOptions.Old, 
+      context: nil)
+  }
+
+  override func observeValueForKeyPath(_ path:String, ofObject obj:AnyObject, 
+    change change:NSDictionary, context context:KVOContext) 
+  {
+    target!.print()
+  }
+}
+
+
+var t = Target()
+var o = Observer()
+println("unobserved")
+// CHECK: unobserved
+t.objcValue = "one"
+t.objcValue = "two"
+println("registering observer")
+// CHECK-NEXT: registering observer
+o.observeTarget(t)
+println("Now witness the firepower of this fully armed and operational panopticon!")
+// CHECK-NEXT: panopticon
+t.objcValue = "three"
+// CHECK-NEXT: swiftValue 42, objcValue three
+t.objcValue = "four"
+// CHECK-NEXT: swiftValue 42, objcValue four