[SceneKit] Add apinotes to swift_private some decls

apinotes/CMakeLists.txt

@@ -23,6 +23,7 @@ set(SWIFT_API_NOTES_INPUTS
   PassKit
   QuartzCore
   QuickLook
+  SceneKit
   SpriteKit
   StoreKit
   TVMLKit

apinotes/SceneKit.apinotes

@@ -0,0 +1,17 @@
+---
+Name: SceneKit
+
+Protocols:
+# The below are methods for which overlays provide better implementations
+- Name: SCNBoundingVolume
+  Methods:
+  - Selector: 'getBoundingBoxMin:max:'
+    SwiftPrivate: true
+    MethodKind: Instance
+  - Selector: 'setBoundingBoxMin:max:'
+    SwiftPrivate: true
+    MethodKind: Instance
+  - Selector: 'getBoundingSphereCenter:radius:'
+    SwiftPrivate: true
+    MethodKind: Instance
+

stdlib/public/SDK/SceneKit/SceneKit.swift

@@ -199,19 +199,19 @@ extension SCNBoundingVolume {
     get {
       var min = SCNVector3Zero
       var max = SCNVector3Zero
-      getBoundingBoxMin(&min, max: &max)
+      __getBoundingBoxMin(&min, max: &max)
       return (min: min, max: max)
     }
     set {
       var min = newValue.min
       var max = newValue.max
-      setBoundingBoxMin(&min, max: &max)
+      __setBoundingBoxMin(&min, max: &max)
     }
   }
   public var boundingSphere: (center: SCNVector3, radius: Float) {
     var center = SCNVector3Zero
     var radius = CGFloat(0.0)
-    getBoundingSphereCenter(&center, radius: &radius)
+    __getBoundingSphereCenter(&center, radius: &radius)
     return (center: center, radius: Float(radius))
   }
 }