st/mesa: implement ARB_copy_image

I wonder if the craziness was worth it.

Reviewed-by: Brian Paul <brianp@vmware.com>

docs/GL3.txt

@@ -153,7 +153,7 @@ GL 4.3, GLSL 4.30:
   GL_ARB_ES3_compatibility                             DONE (all drivers that support GLSL 3.30)
   GL_ARB_clear_buffer_object                           DONE (all drivers)
   GL_ARB_compute_shader                                in progress (jljusten)
-  GL_ARB_copy_image                                    DONE (i965) (gallium - in progress, VMware)
+  GL_ARB_copy_image                                    DONE (i965, radeonsi)
   GL_KHR_debug                                         DONE (all drivers)
   GL_ARB_explicit_uniform_location                     DONE (all drivers that support GLSL)
   GL_ARB_fragment_layer_viewport                       DONE (nv50, nvc0, r600, radeonsi, llvmpipe)

docs/relnotes/11.1.0.html

@@ -45,6 +45,7 @@ Note: some of the new features are only available with certain drivers.
 
 <ul>
 <li>GL_ARB_blend_func_extended on freedreno (a3xx)</li>
+<li>GL_ARB_copy_image on radeonsi</li>
 <li>GL_ARB_gpu_shader_fp64 on r600 for Cypress/Cayman/Aruba chips</li>
 <li>GL_ARB_gpu_shader5 on r600 for Evergreen and later chips</li>
 <li>GL_ARB_shader_stencil_export on i965 (gen9+)</li>