RTT & Clipping is not working

[wouterlucas]

The moment you turn on clipping on a rtt: true node the node disappears.

This is because the new update logic from parent -> children provides the original clipping rectangle, however since the children are part of render to texture the clipping rectangle does not apply as its clipped already as part of the RTT creation.

In the previous implementation children of RTT where given an invalid clipping rectangle to avoid incorrect clipping in Render texture coordinates.