Make pcap-ng the default. Add a compile-time option to prefer pcap-ng or

Make pcap-ng the default. Add a compile-time option to prefer pcap-ng or
pcap.  Add a "-P" capture option which tries to use pcap instead of
pcap-ng ("-P" seemed to be the best option but we may want to use a
different letter).

Update the documentation and release notes.

git-svn-id: http://anonsvn.wireshark.org/wireshark/trunk@37696 f5534014-38df-0310-8fa8-9805f1628bb7