Remove the "-I" flag from dumpcap, and add a "-M" flag used to specify

Remove the "-I" flag from dumpcap, and add a "-M" flag used to specify
that "-D" and "-L" should produce machine-readable output.  Use this to
move an indirect get_pcap_linktype() call from the GUI to dumpcap.

git-svn-id: http://anonsvn.wireshark.org/wireshark/trunk@22367 f5534014-38df-0310-8fa8-9805f1628bb7