If we don't have any of the pcap_datalink_XXX_to_YYY routines,

If we don't have any of the pcap_datalink_XXX_to_YYY routines,
substitute our own (I wrote them all, so I can steal them from the
BSD-licensed libpcap if I want :-)).  This means that
linktype_name_to_val() and linktype_val_to_name() are always available,
and we don't need to #ifdef use of them.

Use pcap_datalink_val_to_description() to get the description for a
particular DLT_ value, rather than mapping the DLT_ value to a
WTAP_ENCAP_ value and getting the description for the latter.

git-svn-id: http://anonsvn.wireshark.org/wireshark/trunk@27074 f5534014-38df-0310-8fa8-9805f1628bb7