* lib/zebra.h: define UINT32_MAX for those systems which do not
provide it.
* bgp_attr.h: define BGP_MED_MAX.
* bgp_route.c: update defines/constants to BGP_MED_MAX.
* bgp_routemap.c: ditto. clean up route_match_metric_compile
slightly to avoid unneccesary XMALLOC.
* bgpd/bgp_routemap.c: attr->med is type u_in32_t, should be
compared with UINT32_MAX
* ospfd/ospfd.c: remove redundant assert
* zebra/rtadv.c: add missing include for zebra/rib.h