Replace struct timeval with struct timespec as the main data type for
timestamps. This will allow the NTP code to work with timestamps in
nanosecond resolution.
In addition to the quadratic function, allow configuration of the
compensation with a file containing list of (temperature, compensation)
points used for linear interpolation and extrapolation.
This is needed to keep sourcestats accurate when the actual frequency is
different from the requested frequency due to clamping (or possibly
rounding in future system drivers).
A new tempcomp directive can be used to specify a file for reading
current temperature, update interval and compensation coefficients. The
clock frequency corrections are applied in local module and are invisible
in upper layers. The measurements and corrections can be logged to
tempcomp.log file.
