added GetNext function; uses same 'infrastructure' as get so accepts multiple oids at once
added GetNext function; uses same 'infrastructure' as get so accepts multiple oids at once

jda/gosnmp,virtuallynathan/gosnmp_virtuallynathan,wdreeveii/gosnmp-sonia,MrSpock/gosnmp,mgenov/gosnmp,jda/gosnmp,MrSpock/gosnmp,mgenov/gosnmp,virtuallynathan/gosnmp_virtuallynathan