ospfd: use LOOKUP() for ospf_packet_type_str

* ospf_packet.h: add proper str/max extern declarations
* ospf_packet.c
  * ospf_packet_type_str: rewrite in "struct message", add max value
  * ospf_packet_add(): use LOOKUP()
  * ospf_write(): ditto
  * ospf_hello(): ditto
  * ospf_read(): ditto
* ospf_dump.h: the declaration does not belong here
* ospf_dump.c
  * ospf_header_dump(): use LOOKUP()
  * show_debugging_ospf(): ditto
4 files changed