% TTSETPERIOD   Set the period of a periodic task.%%  Usage: ttSetPeriod(value)%         ttSetPeriod(value, taskname)%%  Inputs:%    value     Value to be set.%    taskname  Name of a task. If not specified, the call will%              affect the currently running task.%       % See also TTGETX, TTSETX%%       TrueTime, Version 1.4%       Copyright (c) 2006%       Martin Ohlin, Dan Henriksson and Anton Cervin%       Department of Automatic Control, LTH%       Lund University, Sweden