snmppp: bump to version 3.3.4

Changes snmp++v3.3.4:
- Fixed: Incorrect time values conversion in += and -= operators of the
  msec class in msec.cpp.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/snmppp/snmppp.mk

@@ -4,7 +4,7 @@
 #
 ################################################################################
 
-SNMPPP_VERSION = 3.3.3
+SNMPPP_VERSION = 3.3.4
 SNMPPP_SOURCE = snmp++$(SNMPPP_VERSION).tar.gz
 SNMPPP_SITE = http://www.agentpp.com
 SNMPPP_DEPENDENCIES = openssl host-pkgconf