start

(Re)starts the timer, return #f if the timer cannot be started or #t otherwise.

• (send a-wx:timer start m just-once?) -> boolean
      m : small integer
      just-once? = #f : boolean

  The timer's alarm will expire after m milliseconds and notify is called (on an event boundary). If just-once? is #f, the timer will expire every m milliseconds until the timer is explictly stopped; otherwise, the timer will expire only once.