compositor-wayland: Convert fullscreen flag to bool

Signed-off-by: Armin Krezović <krezovic.armin@gmail.com>
Reviewed-by: Quentin Glidic <sardemff7+git@sardemff7.net>
diff --git a/libweston/compositor-wayland.c b/libweston/compositor-wayland.c
index df34f91..d26360e 100644
--- a/libweston/compositor-wayland.c
+++ b/libweston/compositor-wayland.c
@@ -77,7 +77,7 @@
 
 	bool use_pixman;
 	bool sprawl_across_outputs;
-	int fullscreen;
+	bool fullscreen;
 
 	struct theme *theme;
 	cairo_device_t *frame_device;