update HTML and TXT man pages

This change improves ASCII compliance in TXT files (commit be79925 left
hyphen character as 0xe28090, U+2010), updates text in existing HTML and
TXT files to match the latest man pages in libpcap repository and adds
new HTML and TXT files for the following topics:
* pcap-filter
* pcap-linktype
* pcap-savefile
* pcap-tstamp

It was done as follows:

MAN='man -E ascii'
MAN2HTML='man2html -M /cgi-bin/man/man2html'

 # make the terminal have exactly 80 columns in width
for f in ../libpcap/*.3pcap ../libpcap/pcap-config.1; do
 $MAN $f > manpages/`basename $f`.txt
 $MAN2HTML $f > manpages/`basename $f`.html
done

$MAN ../libpcap/pcap-filter.manmisc > manpages/pcap-filter.7.txt
$MAN ../libpcap/pcap-linktype.manmisc > manpages/pcap-linktype.7.txt
$MAN ../libpcap/pcap-savefile.manfile > manpages/pcap-savefile.5.txt
$MAN ../libpcap/pcap-tstamp.manmisc > manpages/pcap-tstamp.7.txt

$MAN2HTML ../libpcap/pcap-filter.manmisc > manpages/pcap-filter.7.html
$MAN2HTML ../libpcap/pcap-linktype.manmisc > manpages/pcap-linktype.7.html
$MAN2HTML ../libpcap/pcap-savefile.manfile > manpages/pcap-savefile.5.html
$MAN2HTML ../libpcap/pcap-tstamp.manmisc > manpages/pcap-tstamp.7.html

 # revert (git checkout) HTML files without meaningful changes
 # remove Content-type header from *.html
 # save changes