draw_idle and draw_rubberband fixes for wxPython on OSX.#3905

tacaswell merged 1 commit intomatplotlib:v1.4.xmatplotlib/matplotlib:v1.4.xfrom

RobinD42:fix-backend_wx-v1.4.xRobinD42/matplotlib:fix-backend_wx-v1.4.xCopy head branch name to clipboard