Export missing vgcontext*.h headers and remove libvgi.mmp due to collision with KhronosRI.
EXPORTS
_ZN25CTGraphicsImageComparison14CompareBitmapsERK5TSizeRK6TPointRK10CFbsBitmapRK4TRgbm @ 1 NONAME
_ZN25CTGraphicsImageComparison14CompareBitmapsERK5TSizeRK6TPointS5_RK10CFbsBitmapS8_m @ 2 NONAME