Added a new input control that smooths the brush stroke.
This option controlled by the menu item Sculpt>Input Control>Smooth Stroke. When enabled, the brush has a delayed effect on the model; a green line is drawn to indicate the smoothed path of the stroke. After ~200 pixels, the first half of the stroke will be applied to the model; the process then repeats, with a new segment of the stroke being applied to the model after every 200 pixels. On mouse up, any remaining portion of the stroke will be applied.
Other changes:
* Added a flags field to SculptData; currently only used for smooth stroke but other flags can be moved into it
* Moved the damaged_rects/verts into SculptSession
* Simplified brush application by moving init_editdata into do_symmetrical_brush_actions
* Removed Averaging from sculpt Input menu; smooth stroke should take its place
TODO:
* Fix display of the smooth line in Partial Redraw mode
* Make the smoothing and delay factors adjustable
* Optimize the stroke application (currently using the old 'dot' style of applying the brush)