* isis_spf.c: Changing cost from uint16_t to uint32_t. Unset

	* isis_spf.c: Changing cost from uint16_t to uint32_t. Unset
	  ISIS_ROUTE_FLAG_ACTIVE flag before running SPF.
	* isisd.[ch]: Separate route tables for different levels. SPF is done
	  separately, but in case of L1L2 area they have to be merged.
	* isis_zebra.c: Set/unset ISIS_ROUTE_FLAG_ZEBRA_SYNC flag correctly in
	  case of adding/removing IPv4 routes.
	* zebra_route.c: Rework route validating process. Merging L1 and L2
	  tables in case of L1L2 area.

        In short - many changes to make SPF work more correctly, add/remove
        to/from RIB also works now. It's still very far from perfect though.