Implement SSVN default values
Implement SSVN default values. Need to be able to define SSVN references with a corresponding default value, as
KILLing certain MWAPI nodes in
^$WINDOW is supposed to restore the default attribute instead of making the node undefined.
KILL will need a way to trigger this, as well as
KVALUE. May be best handled in
symtab(), as thus far, only process-private SSVNs have this requirement.