Blender Git Loki

Fix regression in 2cc5af9c553cfc00b7d4616445ad954597a92d94

The check for undo-depth increment/decrement assumed a newly loaded
window manager would have a different pointer.

This broke bl_animation_fcurves test indirectly,
the change to undo-depth caused the redo panel to attempt to popup
in background mode - which isn't supported.

Now the pointer is unchanged, the undo-depth is assumed to match
the value used when calling the operator.

The undo-depth is now properly maintained between file loads,
which is an improvement on the original behavior which reset it.