Unified multiple definitions of container_of() macro.

Removed duplicate definitions of the container_of() macro and
refactored sources to use the single implementation.

Signed-off-by: Jon A. Cruz <jonc@osg.samsung.com>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Bryce Harrington <bryce@osg.samsung.com>
diff --git a/fullscreen-shell/fullscreen-shell.c b/fullscreen-shell/fullscreen-shell.c
index 9b81212..ab9c420 100644
--- a/fullscreen-shell/fullscreen-shell.c
+++ b/fullscreen-shell/fullscreen-shell.c
@@ -34,6 +34,7 @@
 
 #include "compositor.h"
 #include "fullscreen-shell-server-protocol.h"
+#include "shared/helpers.h"
 
 struct fullscreen_shell {
 	struct wl_client *client;