Provide damage region for screen recording on Raspberry Pi

When trying to do sceen recording using the screenshooter, no screen data
was ever processed because the rpi-renderer never set the previous frames
damage area.

Update the rpi-renderer to copy the necessary data.

Signed-off-by: Shinya Saito <ssaito@igel.co.jp>
Signed-off-by: Tomohito Esaki <etom@igel.co.jp>
Reviewed-by: Bryce Harrington <bryce@osg.samsung.com>

src/rpi-renderer.c

@@ -1410,6 +1410,7 @@ rpi_renderer_repaint_output(struct weston_output *base,
 	/* The frame_signal is emitted in rpi_renderer_finish_frame(),
 	 * so that the firmware can capture the up-to-date contents.
 	 */
+	pixman_region32_copy(&base->previous_damage, output_damage);
 }
 
 static void