Blender Git Loki

IRC bugreport fix: thumb brush works incorrect when using tablet by Dan McGrath (troubled)

Quite silly fix, not sure if it could be smarter with current events/brushes design.
Use pressure_value from first brush step for brushes which don't support strokes -- thumb.
brush, brushes with anchored stroke method.

Should be fixed in nicer way after events redesigning.

P.S. Tried to place pressure saving into invaliants update fuunction, but it seens
that this function wouldn't know about pressure yet.