Update to OOP facilities. * scripts/general/isa.m: Fixed isa so that multiple layers of class hierarchy are reported correctly. * src/variables.cc: Make exist('obj') for objects report correctly. * src/ov-base.h: Added an assign method so ov-class is able to assign structure elements properly. * src/ov-class.h: Assign map elements. * src/ov-class.cc: - Made sure that there are no duplicate classes in parent tree. - Simplified search algorithm for parent classes. - Fixed subsasgn so cls = method(cls,value) works when properly when method is a parent-class method. - Added __isa_parent__ so isa works correctly.