ONCOUNT returns an unscaled REAL FIXED BINARY value specifying
the number of conditions that remain to be handled when an ON-unit
is entered. (See Multiple conditions.) It is in context in any ON-unit,
or any dynamic descendant of an ON-unit.
>>-ONCOUNT-+----+---------------------------------------------->< '-()-'
If ONCOUNT is used out of context, zero is returned.
The BIFPREC compiler option determines the precision of the result returned.