st/mesa: expose ARB_shader_texture_lod if SM3 is supported

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

src/mesa/state_tracker/st_extensions.c

@@ -603,4 +603,8 @@ void st_init_extensions(struct st_context *st)
    else if (screen->get_param(screen, PIPE_CAP_SEAMLESS_CUBE_MAP)) {
       ctx->Extensions.ARB_seamless_cube_map = GL_TRUE;
    }
+
+   if (screen->get_param(screen, PIPE_CAP_SM3)) {
+      ctx->Extensions.ARB_shader_texture_lod = GL_TRUE;
+   }
 }