samples/wx/hello_wx.py stutters on slower desktop monitors

[cmbruns]

I resolved most of the problem in issue #15 (I believe) by using single-buffering rather than double-buffering for the desktop screen mirror window in the glfw, glut, qt, and sdl frameworks. But I could not relieve the stuttering using the wx framework, without eliminating the on-screen mirror. So this issue records this one remaining problem.