cosmetic: replace boolean function return values with bool

For functions that test if something is true/valid and return a 1
or 0, it makes sense to switch to bool.

Reviewed-by: Bryce Harrington <b.harrington@samsung.com>
Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
diff --git a/src/compositor.c b/src/compositor.c
index 4540911..ac5bda2 100644
--- a/src/compositor.c
+++ b/src/compositor.c
@@ -1370,22 +1370,22 @@
 	weston_view_geometry_dirty(view);
 }
 
-WL_EXPORT int
+WL_EXPORT bool
 weston_view_is_mapped(struct weston_view *view)
 {
 	if (view->output)
-		return 1;
+		return true;
 	else
-		return 0;
+		return false;
 }
 
-WL_EXPORT int
+WL_EXPORT bool
 weston_surface_is_mapped(struct weston_surface *surface)
 {
 	if (surface->output)
-		return 1;
+		return true;
 	else
-		return 0;
+		return false;
 }
 
 static void
@@ -2626,20 +2626,20 @@
 	sub->has_cached_data = 1;
 }
 
-static int
+static bool
 weston_subsurface_is_synchronized(struct weston_subsurface *sub)
 {
 	while (sub) {
 		if (sub->synchronized)
-			return 1;
+			return true;
 
 		if (!sub->parent)
-			return 0;
+			return false;
 
 		sub = weston_surface_to_subsurface(sub->parent);
 	}
 
-	return 0;
+	return true;
 }
 
 static void