This new approach (CLOCK_CONF_ACCURATE=0) was not as inaccurate
as originally thought. In fact, it has pretty much the same
accuracy as the old, stack-hungry version.
* Renamed the define from CLOCK_CONF_ACCURATE (1: old) to
CLOCK_CONF_STACK_FRIENDLY (1: new) to stop implying
that one is more accurate than the other.
* Using CLOCK_CONF_STACK_FRIENDLY by default.
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