net-snmp-5.7.2: fix CVE-2014-2285

The perl_trapd_handler function in perl/TrapReceiver/TrapReceiver.xs
in Net-SNMP 5.7.3.pre3 and earlier, when using certain Perl versions,
allows remote attackers to cause a denial of service (snmptrapd
crash) via an empty community string in an SNMP trap, which triggers
a NULL pointer dereference within the newSVpv function in Perl.

http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2014-2285


Signed-off-by: yzhu1 <yanjun.zhu@windriver.com>
Signed-off-by: Roy Li <rongqing.li@windriver.com>
Signed-off-by: Joe MacDonald <joe@deserted.net>