This creates a new Overlay object. Overlays represent a basic
interface for putting YUV image data into the graphics card's
video overlay planes. This is a low level object intended for
use by people who know what they are doing, and have pregenerated
YUV image data.
The pixeltype argument must be one of the pygame constants;
YV12_OVERLAY, IYUV_OVERLAY, YUV2_OVERLAY, UYVY_OVERLAY, or YVYU_OVERLAY.