Fix app icon rendering on iOS 6

vlc-ios/Images.xcassets/AppIcon.appiconset/Contents.json

@@ -100,5 +100,8 @@
   "info" : {
     "version" : 1,
     "author" : "xcode"
+  },
+  "properties" : {
+    "pre-rendered" : true
   }
 }