snapshot length before writing them to the output file; this may come in
handy if you are translating the file to a different format so that it
can be read by a program that can't handle packets above a certain size
(e.g., the snoop in Solaris 2.5.1 or 2.6, which reject Ethernet packets
larger than the Ethernet MTU, and thus can't handle gigabit Ethernet
captures using jumbo frames).
svn path=/trunk/; revision=1891
Guy Harris