Add initial prototype.

3-mid/opengl/source/lean/opengl-frustum.ads

@@ -0,0 +1,12 @@
+package openGL.Frustum
+--
+-- Provide frustum operations.
+--
+is
+
+   type Plane_Id    is (Left, Right, High, Low, Near, Far);
+   type Plane_array is array (Plane_Id) of openGL.Geometry_3d.Plane;
+
+   procedure normalise (Planes : in out Plane_array);
+
+end openGL.Frustum;