Sequential Rendering

Flagging sequential rendering has been slightly modified. The kOfxImageEffectInstancePropSequentialRender property has had a third allowed state added, which indicate that a plugin would prefer to be sequentially rendered if possible, but need not be.

The kOfxImageEffectInstancePropSequentialRender propery has also been added to the host descriptor, to indicate whether the host can support sequential rendering.

The new property kOfxImageEffectPropSequentialRenderStatus is now passed to the render actions to indicate that a host is currently sequentially rendering or not.