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 * CLOCKs: The POSIX standard calls for a couple of clocks and allows us
 *          to implement others.  This structure defines the various
 *          clocks and allows the possibility of adding others.  We
 *          provide an interface to add clocks to the table and expect
 *          the "arch" code to add at least one clock that is high
 *          resolution.  Here we define the standard CLOCK_REALTIME as a
 *          1/HZ resolution clock.