Update ping(8) code and manpage to the newest ones from FreeBSD.
Besides many small fixes this brings in some new features:
* -D to set Don't Fragment bit
* -G, -g and -h for sweeping pings
* -M for using ICMP_MASKREQ or ICMP_TSTAMP instead of ICMP_ECHO
* -o to exit successfully after receiving one reply packet
* -W to set time to wait for a reply for each packet sent
* -z to set TOS
Significant part of diff not related to the new features is coming
from reordering command line options into alphabetic order.
Obtained-from: FreeBSD