Remove the concept of stableRoots.

Remove the concept of stableRoots.

StableRoots opened new possibilities in the world
of plugins with their ability to link partially
applied closures against object code.
Exporting '(fn pluginwideState)' severely reduced
the complexity of HIDE's plugin system. The previous
system of global variables was both fragile and hard
to scale.

Good bye, StableRoots. We sure had some fun.