Since deraadt@ remembers seeing strdup() on one particular 4.2BSD machine,
i looked a bit closer and found instances before Reno, so correct HISTORY.

References:
http://minnie.tuhs.org/cgi-bin/utree.pl?file=4.1cBSD/usr/src/ucb/dbx/defs.h
http://minnie.tuhs.org/cgi-bin/utree.pl?file=4.3BSD/usr/src/etc/inetd.c
http://minnie.tuhs.org/cgi-bin/utree.pl?file=4.3BSD-Reno/src/lib/libc/string/strdup.c

ok deraadt@