Add initial prototype.

3-mid/opengl/source/lean/buffer/opengl-buffer-indices.ads

@@ -0,0 +1,7 @@
+with
+     openGL.Buffer.general;
+
+package openGL.Buffer.indices is new openGL.Buffer.general (base_Object   => Buffer.element_array_Object,
+                                                            Index         => long_Index_t,
+                                                            Element       => Index_t,
+                                                            Element_Array => Indices);