Make server and all clients run desync checks if a client desyncs.

src/command_type.h

@@ -343,6 +343,8 @@ enum Commands {
 	CMD_REMOVE_PLAN_LINE,
 	CMD_CHANGE_PLAN_VISIBILITY,
 
+	CMD_DESYNC_CHECK,                 ///< Force desync checks to be run
+
 	CMD_END,                          ///< Must ALWAYS be on the end of this list!! (period)
 };