bgpd: justify checks for IPv4 class D/E

* lib/prefix.h
  * IPV4_CLASS_DE(): make consistent with counterpart macros
* bgp_packet.c
  * bgp_open_receive(): test using macro instead of ">="
* bgp_route.c
  * bgp_update_rsclient(): idem
  * bgp_update_main(): idem
3 files changed