Blender Git Loki

Fix T39486, screwed object bevel made bevel amount go out of control.

There is an adjustment pass in bevel that tries to make the bevel
widths at either end of a beveled edge as equal as possible.
When there are hundreds of beveled edges end-to-end, these adjustments
can accumulate out of control and result looks awful.
Yet the adjustment pass is sometimes needed to avoid equally awful
appearances in other cases (see the "Bent test" in the bevel regression
tests).
This change uses the 'Clamp overlap' flag of bevel (on by default in
the modifier, not in the tool) to limit the amount of adjustment to within
10% of the desired width. When the flag is off, there is no limit to the
adjustment.