override token in snmpd.conf does not allow snmpset on OID

When you try to SET a non-writable OID such as
sysDescr, it returns a generic error, which does not
tell the user what really went wrong.

This bug was found using net-snmp 5.0.9 (the
V5-0-patches branch), running Solaris 10 on sparc
64-bit and intel 32-bit.

Define the following line in the snmpd.conf file:
override -rw sysDescr.0 octet_str "my descr value"

When an snmpget is done on the OID the override value
"my descr value" is returned. -- correct behavior

When an snmpset is done on the OID, a debug message is
displayed and the value is not truly set for the oid.

A patch is provided to fix this problem. The intent of
the code change is to have the code return a more
descriptive error code, in this case, notWritable,
which the core agent code would then translate to
noSuchName if SNMPv1 is being used. Note that readOnly
cannot be used because of the way the SNMP
specifications were written.

net-snmp.patch is the patch file.

Files changed in the net-snmp V5-0-Patches branch
(net-snmp 5.0.9) are the following:

net-snmp/agent/mibgroup/mibII/system_mib.c