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>

clients/clickdot.c

@@ -40,6 +40,7 @@
 #include <wayland-client.h>
 
 #include "window.h"
+#include "shared/helpers.h"
 
 struct clickdot {
 	struct display *display;

clients/desktop-shell.c

@@ -45,6 +45,7 @@
 #include "window.h"
 #include "shared/cairo-util.h"
 #include "shared/config-parser.h"
+#include "shared/helpers.h"
 
 #include "desktop-shell-client-protocol.h"
 

clients/window.h

@@ -33,10 +33,6 @@
 #include "shared/zalloc.h"
 #include "shared/platform.h"
 
-#define container_of(ptr, type, member) ({				\
-	const __typeof__( ((type *)0)->member ) *__mptr = (ptr);	\
-	(type *)( (char *)__mptr - offsetof(type,member) );})
-
 struct window;
 struct widget;
 struct display;