adjtime()

[Till Straumann]

Currently, adjtime() basically steps the time (albeit not
backwards if IRC) and this only if the requested difference
is bigger than a full clock tick.

IMO it would make sense to improve this implementation by

- gradually adjusting the clock, i.e., absorbing the requested
   delta over multiple clock ticks.
- allow small adjustments (especially on architectures
   with a high-resolution clock)

I know that adjtime() is not posix but AFAIK there is nothing else.

Ultimate goal would be letting an NTP client use adjtime().

Maybe even a better idea would be incorporating the Mills
algorithm into the system clock and add adjtimex() for tuning
it with an NTP client.

RFC
- Till