paned layout: #beNotResizable does not work in Morphic

[jecisc]

[JanBliznicenko]

Just adding that #beNotShrinkable in SpPanedConstraints has no effect either. No method of SpPanedConstraint has any user. It would be very useful if I could pick which pane should react to outside sources of resize (like window resize), not always the right one in case of fixed splitter position and both in case of proportional splitter position.