checked for mac compatibility:    added ncells forwards for all available specializations: domain, segment, element_t
checked for mac compatibility:
   added ncells forwards for all available specializations: domain, segment, element_t

   removed previously compatitbily ncells forward (was commented, is obsolete by now)

   tested on linux and mac - works

viennagrid/viennagrid-dev,viennagrid/viennagrid-dev,viennagrid/viennagrid-dev