st/mesa: expose KHR_texture_compression_astc_sliced_3d

This is ASTC 2D LDR allowing texture arrays and 3D, compressing each
slice as a separate 2D image. Tested by piglit. Trivial.

docs/features.txt

@@ -326,7 +326,7 @@ Khronos, ARB, and OES extensions that are not part of any OpenGL or OpenGL ES ve
   GL_EXT_texture_norm16                                 DONE (i965, r600, radeonsi, nvc0)
   GL_KHR_blend_equation_advanced_coherent               DONE (i965/gen9+)
   GL_KHR_texture_compression_astc_hdr                   DONE (i965/bxt)
-  GL_KHR_texture_compression_astc_sliced_3d             DONE (i965/gen9+)
+  GL_KHR_texture_compression_astc_sliced_3d             DONE (i965/gen9+, radeonsi)
   GL_OES_depth_texture_cube_map                         DONE (all drivers that support GLSL 1.30+)
   GL_OES_EGL_image                                      DONE (all drivers)
   GL_OES_EGL_image_external                             DONE (all drivers)

docs/relnotes/18.3.0.html

@@ -58,6 +58,7 @@ Note: some of the new features are only available with certain drivers.
 <li>GL_EXT_disjoint_timer_query on radeonsi and most other Gallium drivers (ES extension)</li>
 <li>GL_EXT_vertex_attrib_64bit on i965, nvc0, radeonsi.</li>
 <li>GL_EXT_window_rectangles on radeonsi.</li>
+<li>GL_KHR_texture_compression_astc_sliced_3d on radeonsi.</li>
 </ul>
 
 <h2>Bug fixes</h2>

src/mesa/state_tracker/st_extensions.c

@@ -810,7 +810,8 @@ void st_init_extensions(struct pipe_screen *screen,
           PIPE_FORMAT_BPTC_RGB_FLOAT,
           PIPE_FORMAT_BPTC_RGB_UFLOAT } },
 
-      { { o(KHR_texture_compression_astc_ldr) },
+      { { o(KHR_texture_compression_astc_ldr),
+          o(KHR_texture_compression_astc_sliced_3d) },
         { PIPE_FORMAT_ASTC_4x4,
           PIPE_FORMAT_ASTC_5x4,
           PIPE_FORMAT_ASTC_5x5,
@@ -841,7 +842,8 @@ void st_init_extensions(struct pipe_screen *screen,
           PIPE_FORMAT_ASTC_12x12_SRGB } },
 
       /* ASTC software fallback support. */
-      { { o(KHR_texture_compression_astc_ldr) },
+      { { o(KHR_texture_compression_astc_ldr),
+          o(KHR_texture_compression_astc_sliced_3d) },
         { PIPE_FORMAT_R8G8B8A8_UNORM,
           PIPE_FORMAT_R8G8B8A8_SRGB } },