systray: Sort icons in the correct order when an icon is empty and order is right2left

src/systray/systraybar.h

@@ -14,6 +14,8 @@
 #include "area.h"
 #include "timer.h"
 #include <X11/extensions/Xdamage.h>
+#include <time.h>
+#include <sys/time.h>
 
 // XEMBED messages
 #define XEMBED_EMBEDDED_NOTIFY		0
@@ -47,6 +49,7 @@ typedef struct
 	int empty;
 	int pid;
 	int chrono;
+    struct timespec time_last_render;
 } TrayWindow;