EVTcancel_value_call(). EVTnew_value_call() specifies a function
to be called for each confirmed new value produced on an XSPICE
event node. To be used to add event node support for iplot.
to a code model, there is no longer a reference to the value of the event
at the head of the free list. That allows all such free lists (with the
same data type) to be combined, probably improving performance.
This is in preparation for full implementation of inertial delay for
digital nodes.
memory (one state per time step added). Memory of
previous time steps is not recovered.
Patch #109 by Giles Atkinson reduces memory consumption
dramatically (> factor of 10).