SNMP state changes are now handled by snmp_set_state() functions.
The registration structure and related variables are renamed to remove
confusion.
Manipulation of BGP peers, a reference to BGP protocol structures, is improved
by new functions that encapsulate raw hash table macros (moved from snmp.h).
IPv4 addresses now used by bgp_mib.c because BGP4-MIB does not support IPv6
addresses.
Configuration grammar rules are revised.
We now use DBG() and TRACE() macros to output information about SNMP state
chagnes and about received and transmitted packets.
Pieces of old code are removed, minor bugfixes are included. Large debug string
array are removed.
