libweston: Add functions to modify disable_planes counter for an output

The member disable_planes of weston_output signifies the recording
status of the output, and is incremented and decremented from various
places. This patch provides helper functions to increment and decrement
the counter. These functions can then be used to do processing, before
and after the recording has started or stopped.

Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>

tests/weston-test.c

@@ -443,7 +443,7 @@ test_screenshot_frame_notify(struct wl_listener *listener, void *data)
 	int32_t stride;
 	uint8_t *pixels, *d, *s;
 
-	output->disable_planes--;
+	weston_output_disable_planes_decr(output);
 	wl_list_remove(&listener->link);
 	stride = l->buffer->width * (PIXMAN_FORMAT_BPP(compositor->read_format) / 8);
 	pixels = malloc(stride * l->buffer->height);
@@ -539,7 +539,7 @@ weston_test_screenshot_shoot(struct weston_output *output,
 	wl_signal_add(&output->frame_signal, &l->listener);
 
 	/* Fire off a repaint */
-	output->disable_planes++;
+	weston_output_disable_planes_incr(output);
 	weston_output_schedule_repaint(output);
 
 	return true;