Set constructor properly in createReactNativeComponentClass

Summary:
Without this, the displayName property wasn't found when looking at
`.constructor` on a component instance. Fixes facebook/react-devtools#92.
Closes https://github.com/facebook/react-native/pull/1471
Github Author: Ben Alpert <balpert@fb.com>

Test Plan:
Used devtools on MoviesApp and saw RCTView instead of Unknown:

{F22491590}

Libraries/ReactNative/createReactNativeComponentClass.js

@@ -36,6 +36,7 @@ var createReactNativeComponentClass = function(
   };
   Constructor.displayName = viewConfig.uiViewClassName;
   Constructor.prototype = new ReactNativeBaseComponent(viewConfig);
+  Constructor.prototype.constructor = Constructor;
 
   return Constructor;
 };