Add CVE-2002-0380 (read overflow) vulnerability to tcpdump.

This is a vulnerability that allows remote attackers to cause a denial
of service (crash) with a malformed NFSv2 packet.  The malformed packet
is generated with 'nfs.py' and should cause tcpdump to core dump on a
segmentation fault and exit. CHERI_TCPDUMP_VULNERABILITY must be defined
to activate the vulnerable code.