Function: snmpv2-mode

Major mode for editing SNMPv2 MIBs.
Expression and list commands understand all C brackets.
Tab indents for C code.
Comments start with -- and end with newline or another --.
Delete converts tabs to spaces as it moves back.

Uses keymap `snmp-mode-map', which is not currently defined.

Turning on snmp-mode runs the hooks in `snmp-common-mode-hook', then `snmpv2-mode-hook'. (fn)