Many UN*Xes come with libpcap, so you might not have to install

Many UN*Xes come with libpcap, so you might not have to install
tcpdump.org's libpcap in order to build tcpdump.org's tcpdump (the
configure script doesn't assume the latest version of libpcap, so it
should be possible to build tcpdump with older versions of libpcap).

By default, tcpdump is installed with universal execute permissions, and
no special privileges; that way, anybody can use it to read a capture.

Remove the comments about capture permissions, as it applies only to
systems using BPF.  The tcpdump man page gives the gory details of
capture permissions; refer users there.

Remove the comment about libpcap; it's in the libpcap INSTALL.txt, where
it belongs.