[AGENT++] Minor typo in library reference in agentx++-2.pc.in

[Isaac Nickaein]

Hi,

There is a typo in agentx++-2.pc.in of AgentX++ 2.0.9 referencing
snmp++ library incorrectly. The line saying:

Libs: -L${libdir} -lsnnp++ -lagent++ -lagentx++

should be:

Libs: -L${libdir} -lsnmp++ -lagent++ -lagentx++


Bests,
Isaac