[RTEMS Project] #4772: Remove use of interval from rtems_task_wake_after() documentation

[RTEMS trac]

#4772: Remove use of interval from rtems_task_wake_after() documentation
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  Reporter:  Chris Johns  |      Owner:  (none)
      Type:  enhancement  |     Status:  new
  Priority:  normal       |  Milestone:  6.1
 Component:  doc          |    Version:  6
  Severity:  normal       |   Keywords:
Blocked By:               |   Blocking:
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 The Classic API documentation for `rtems_task_wake_after()` refers to an
 **interval** while the call accepts `ticks`. The exact interval is not
 known because the period of time to next tick is not known when the call
 is made.

 1. Clarify the wording

 2. Recommend new applications use the POSIX based calls `nanosleep()` and
 `clock_nanosleep()` for applications that have intervals in a time base
 rather than system ticks.

 The [https://gitlab.com/nsf-noirlab/gemini/rtsw/epics-base/epics-
 base/-/issues/30 Gemini, Verify the fidelity of RTEMS System Tick] issue
 provides some back ground to this change.

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Ticket URL: <http://devel.rtems.org/ticket/4772>
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