for AIX 5.x's non-standard libpcap, where "pcap_datalink()" doesn't
return DLT_ values, it returns RFC 1573 ifType values.
Put that wrapper, and the routine to get the interface list, in a
separate file, for packet-capture utility routines, so not everybody who
includes "util.h" needs to include <pcap.h>.
Fix up the Wiretap hack for dealing with said incompatibility to use the
correct ifType value for Token Ring.
svn path=/trunk/; revision=4184
Guy Harris