Changeset e8918ec in rtems for c/src/lib/libbsp

Patch from Eric Norum <eric@…> to change to gen68360 clock handling.

I got tired of having strange clock rates (e.g. #define
CONFIGURE_MICROSECONDS_PER_TICK 52489) and drifting times-of-day with
the gen68360 BSP so I changed the way the programmable-interval clock
interrupt works. The new version will have some jitter in the intervals
between individual calls to the rtems_clock_tick routine, but the
long-term average will match the CONFIGURE_MICROSECONDS_PER_TICK