Drivers may need to loop over the allocated screens during PreInit, for example to consolidate xorg.conf options that apply to a GPU device as a whole. Currently, this works for protocol screens becuase x86Screens is exported, but does not work for GPU screens.
Export xf86GPUScreens and xf86NumGPUScreens for consistency with xf86Screens and xf86NumScreens.
Signed-off-by: Aaron Plattner aplattner@nvidia.com