start using texture sets

There are really two main uses of texture sets: checking if a dmabuf
is importable, and actually importing it for the client buffer's
texture

include/wlr/types/wlr_buffer.h

@@ -142,7 +142,7 @@ struct wlr_client_buffer {
 	 * The buffer's texture, if any. A buffer will not have a texture if the
 	 * client destroys the buffer before it has been released.
 	 */
-	struct wlr_texture *texture;
+	struct wlr_texture_set *texture_set;
 	/**
 	 * The buffer this client buffer was created from. NULL if destroyed.
 	 */

include/wlr/types/wlr_linux_dmabuf_v1.h

@@ -63,6 +63,9 @@ struct wlr_linux_dmabuf_v1 {
 
 	int main_device_fd; // to sanity check FDs sent by clients, -1 if unavailable
 
+	// This is only set when the compositor isn't providing a custom renderer.
+	struct wlr_renderer *main_renderer;
+
 	struct wl_listener display_destroy;
 
 	bool (*check_dmabuf_callback)(struct wlr_dmabuf_attributes *attribs, void *data);