Auxiliary class data structure

A structure provided by the SOM API to support efficient static access to class-specific information used in dealing with SOM objects. The structure's name is CClassData. Its first component (parentMtab) is a list of parent-class method tables (used to support efficient parent method calls). Its second component (instanceDataToken) is the instance token for the class (generally used to locate the instance data introduced by method procedures that implement methods defined by the class).