Add preliminary support for multiple layered drawing surfaces.
Allows, for example, static content to be loaded into one layer and
remain unmodified while the above layer contains animations.
Particularly useful for drawing PNG or JPEG UI elements which are
then overdrawn with text or animated elements, without paying the
cost of loading/decoding every frame.
HACK: Adds PicoGraphics_Pen1BitY to work around the UC8151 weird addressing.
TODO: Replace hack with an in-place transform to UC8151 pixel order from Pen1Bit.