* Compo node backdrop works again.
* Compo node previews and backdrop now get correct color management
float to byte conversion.
* Compo nodes got unecessarily recalculated while moving nodes.
* Fix compo node viewer nodes not getting activated correctly.
* Main compo node preview render computations are now outside of
mutex lock, so better for multithreading.
* Tex node outputs did not work in some files loaded from 2.4.
* Change RNA updates to take into account groups that may be shared
between multiple node trees.
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