Several filter changes. (Pavel, please check if they are OK.)

   o  Changed parameters of f_run. Changed rtein+rteout pair to rte pointer
      passed by reference, added ea_list of temporary attrs again passed
      by reference and finally added a pointer to memory pool for storing
      temporary data (new ea_lists's, temporary rta's etc.).
   o  Re-ordered result codes, so that all accepts come before all rejects.
   o  Introduced FILTER_ACCEPT and FILTER_REJECT dummy values (will be
      used in protocol configurations).
   o  Added filter_name() which returns name of a filter or ACCEPT/REJECT
      for the dummies.