Asynchronous timer services.

Five types of asynchronous request are supported by the class:

1. Requesting an event after a specified interval

2. Requesting an event at a specified system time

3. Requesting a timer event on a specific second fraction

4. Requesting an event if an interval elapses with no user activity.

5. Requesting an event after a specified interval, to a resolution of 1ms.

Each of these requests can be cancelled.

The timer exists from its creation, following a call to RTimer::CreateLocal(), until it is destroyed by a call to the Close() member function of the base class RHandleBase.

This class is ultimately implemented in terms of the nanokernel tick, and therefore the granularity of the generated events is limited to the period of this timer. This is variant specific, but is usually 1 millisecond.

Note that the CTimer active object uses an RTimer.