bgpd: general MP/SAFI improvements

This fixes some minor mixups particularly in MPLS-related SAFIs, as well
as doing some stylistic changes & adding comments.

Signed-off-by: Lou Berger <lberger@labn.net>
Reviewed-by: David Lamparter <equinox@opensourcerouting.org>
diff --git a/bgpd/bgp_route.h b/bgpd/bgp_route.h
index 5a93b44..8e9bcbd 100644
--- a/bgpd/bgp_route.h
+++ b/bgpd/bgp_route.h
@@ -196,7 +196,7 @@
 extern void bgp_info_set_flag (struct bgp_node *, struct bgp_info *, u_int32_t);
 extern void bgp_info_unset_flag (struct bgp_node *, struct bgp_info *, u_int32_t);
 
-extern int bgp_nlri_sanity_check (struct peer *, int, u_char *, bgp_size_t);
+extern int bgp_nlri_sanity_check (struct peer *, int, safi_t, u_char *, bgp_size_t);
 extern int bgp_nlri_parse (struct peer *, struct attr *, struct bgp_nlri *);
 
 extern int bgp_maximum_prefix_overflow (struct peer *, afi_t, safi_t, int);