Report failures of "pcap_stats()", as tcpdump does.

Report failures of "pcap_stats()", as tcpdump does.

Print the "Capturing on <interface>" message, the running count of
packets captured, and error messages to the standard error in Tethereal,
so that you can pipe the output of a live capture that's printing
packets to a program or script without that script having to worry about
parsing stuff other than dissected packet summaries or details (tcpdump
does the same).

git-svn-id: http://anonsvn.wireshark.org/wireshark/trunk@3017 f5534014-38df-0310-8fa8-9805f1628bb7