ControlContext :: startTimer - Start timer

A timer can be started for a control in order to sent timer events to the control. Timer events will be generated according to the interval time passed to the function in the iWait parameter. Passing 0 as interval causes the system to sent a timer event each time, when all other events have been processed.

Timer should be initialized in the doAfterOpen() handler function.

Timer events are sent until calling stopTimer() or destroying the control. Timer events can be handled by implementing a doTimer() handler function in the context class, which had started the timer.