Added threading lock around unsafe part of do_makeDispListCurveTypes
(parts which touches Curve->bev and Curve->path). Namely it means
pre-tesselation modifiers, bevel, path and non-modified display
list will be calculated inside a locked thread.
Post-tessellation modifiers will eb calculated outside of locked
thread, which means heavy constructive or deformation modifiers
applying on tesselated spline will be nicely threaded.
This makes it possible to use threaded object update by default
in the branch, so everyone could start testing it.
d50ff36d3d