TODO

* Merge length calculation and encoding in mib.c and protocol.c

Some length calculation and encoding code exists in both mib.c and
protocol.c with only slight differences; try to merge that

* Audit encoding functions in mib.c

The encode functions in mib.c do not check the size; this can be a
problem when forgetting to initialize octet string MIB variables with
their maximum length (only for strings, not for integers)

* Check system MIB against RFC for missing required OIDs

Check the relevant RFCs for the SNMP V1 and V2 MIBs and which parts of
the system MIB are must be included

* Audit FreeBSD backend, missing functionality still

The FreeBSD backend has received native support in v1.3 so it does not
need to use Linux /proc compat anymore.  However, some parts are not
fully implemented yet.

* Add SNMPv3 support, RFC2574/RFC3414

At least user-based security.