Allow changing software skinning at runtime.
Allow changing prescale uv at runtime.
Move GLLost to NativeInit/NativeShutdown.

Otherwise, we clear the registered holders when the display turns off, and
never remember them.  This causes the vertex cache to stop working, for
example.
Merge pull request #6459 from unknownbrackets/gllost-fix

Move GL lost manager to NativeInit/NativeShutdown
Merge pull request #6456 from unknownbrackets/gpu-minor

Allow changing software skinning and prescale uv at runtime