DBStructDef :: AddDefinedMember - - internal feature (not documented)
Return value:  Success ( logical  )
Implementation details
logical 
DBStructDef  :: AddDefinedMember ( NString &prop_names, fmcb *fmcbptr, FunctionTypes &var_type )
- prop_names
 - Property name
The property name is passed as 0-terminated string. It may contain a property path that consists of a sequence of property names. 
- fmcbptr - Pointer to field metadata
- var_type - - internal feature (not documented)

