Exception in PanelSkin on SWF target

In a test case like #1140, run in fdb on SWF target, you get this exception when instantiating PanelSkin (on the way out of the constructor):

```
[Fault] exception, information=ReferenceError: Error #1069: Property http://www.adobe.com/2006/flex/mx/internal::setupBindings not found on spark.skins.spark.PanelSkin and there is no default value.
at spark.skins.spark::PanelSkin()
at spark.components.beads::SparkSkinScrollingViewport/set strand()[/org/apache/royale/0.9.8/spark/components/beads/SparkSkinScrollingViewport.as:66]
```

But skins work, in general, like creating a custom skin on your Application. Don't know what's so special about PanelSkin that causes it to not satisfy the ``setupBindings`` that the compiler wants (at runtime).

Reproduce the exception described in #1140 using fdb on the SWF target while instantiating spark.skins.spark.PanelSkin. Start with PanelSkin and the setter at org/apache/royale/0.9.8/spark/components/beads/SparkSkinScrollingViewport.as:66; done means PanelSkin no longer raises the missing setupBindings error while other skins continue to work.

Written by the indexing model from the issue text.