update HTML and TXT man pages

updated manpages:
* pcap-savefile(5)
* pcap_datalink(3pcap)
* pcap_get_tstamp_precision(3pcap)
* pcap_is_swapped(3pcap)
* pcap_list_datalinks(3pcap)
* pcap_set_tstamp_precision(3pcap)
* pcap_snapshot(3pcap)

new manpages:
* pcap_get_tstamp_precision(3pcap)
* pcap_set_tstamp_precision(3pcap)