Returns
            an integer containing the number of objects (entities) in a selection set
         
         
         Arguments
         
- ss
 
            - 
               
            
 
         
         Return Values
         
         An integer. 
         
         Examples
         
         Add the last object to
            a new selection set:
         
         Command: (setq
               sset (ssget "L"))
         <Selection set:
            8>
         
         Use sslength to determine
            the number of objects in the new selection set:
         
         Command: (sslength
               sset)
         1