Expand the introductory discussion to:

Expand the introductory discussion to:

	note at the beginning that tcpdump can write to a save file
	rather than printing a dissection of the packet, and can read
	from a saved file rather than from a network interrface;

	indicate what causes tcpdump to stop capturing (i.e., that,
	unless you've run it with "-c", you have to ^C or "kill" it);

	discuss the meanings of the packet counts it prints;

	indicate that ^T can be used on some OSes to get those packet
	counts while a capture is in progress;

	note that the special privileges required on various OSes are
	required only when capturing packets, not when reading a saved
	capture file;

	note that on at least some versions of Solaris you apparently
	have to be root in order to do a promiscuous capture.

Consistently use italics to mark tcpdump's name.