This adds the runtime support for class properties that are classes
to be arrayed. Add a means to define the dimensions of a property
in the vvp format, and add functions for setting/extracting elements
of a property.
This provides the ivl_target.h interface for class definitions
and expressions, the vvp code generator support for class objects
and properties, and the vvp run time support. Trivial class objects
now seem to work.
Stephen Williams