Memory Leak Fix for Zabbix SNMP Pollers

[Palmertree]

I have found why my SNMP pollers were leaking memory. I wanted to share this with everyone because this might be a problem for a lot of people and it took me a few days to figure this out. The problem is not in the Zabbix code but the NET-SNMP libraries. There is a major memory leak in the libraries for "NET-SNMP Version 5.4". I was able to determine this by running "Valgrind" and saw the "varbinds" leaking like crazy. NET_SNMP version 5.4 is used in most yum installs. Net-SNMP Version 5.4.1 fixes these memory leaks. I had to down load the newest version and compile it. After installing version 5.4.1 of NET-SNMP you must recompile Zabbix Pre 1.4.3 (do not use 1.4.2, has a memory leak in the trappers).

NET-SNMP Release Notes
Release Name: 5.4.1
Notes:
*5.4.1*

snmplib:
- [BUG 1619827]: link libraries against needed external libraries
- [PATCH 1616912]: fix memory leak in UDP transport code
- [PATCH 1592706]: fix memory leak when cloning varbinds