#1326 Fix for memory leak in ip forwarding table

[Sam Tannous]

As reported (and fixed!) by Christian Krause in bug #2503 https://sourceforge.net/p/net-snmp/bugs/2503/, there is a memory leak seen after continuous snmpwalks of the ip-mib in the ip forwarding tables (1.3.6.1.2.1.4). With 5000 static routes installed, snmpd memory consumption rises from about 0.5% to
over 2.5% in two hours on an amd64 workstation with snmpwalks.

[Niels Baggesen]

Thank for the patch! It has been applied to the active branches.