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.