ping: main.c: Consistent use of white space/tabs

[jlduran]

If a user has tabs set at a value other than 8, the output of the usage may not be consistently aligned.

% tabs -2

Before:

% ping
usage:
  ping [-4AaDdfHnoQqRrv] [-C pcp] [-c count] [-G sweepmaxsize]
      [-g sweepminsize] [-h sweepincrsize] [-i wait] [-l preload]
      [-M mask | time] [-m ttl] [-P policy] [-p pattern] [-S src_addr]
      [-s packetsize] [-t timeout] [-W waittime] [-z tos] IPv4-host
  ping [-4AaDdfHLnoQqRrv] [-C pcp] [-c count] [-I iface] [-i wait]
      [-l preload] [-M mask | time] [-m ttl] [-P policy] [-p pattern]
      [-S src_addr] [-s packetsize] [-T ttl] [-t timeout] [-W waittime]
            [-z tos] IPv4-mcast-group
  ping [-6AaDdfHnNoOquvyY] [-b bufsiz] [-c count] [-e gateway]
            [-I interface] [-i wait] [-k addrtype] [-l preload] [-m hoplimit]
            [-p pattern] [-P policy] [-S sourceaddr] [-s packetsize] [-t timeout]
      [-W waittime] [-z tclass] [IPv6-hops ...] IPv6-host

After:

% ping
usage:
  ping [-4AaDdfHnoQqRrv] [-C pcp] [-c count] [-G sweepmaxsize]
      [-g sweepminsize] [-h sweepincrsize] [-i wait] [-l preload]
      [-M mask | time] [-m ttl] [-P policy] [-p pattern] [-S src_addr]
      [-s packetsize] [-t timeout] [-W waittime] [-z tos] IPv4-host
  ping [-4AaDdfHLnoQqRrv] [-C pcp] [-c count] [-I iface] [-i wait]
      [-l preload] [-M mask | time] [-m ttl] [-P policy] [-p pattern]
      [-S src_addr] [-s packetsize] [-T ttl] [-t timeout] [-W waittime]
      [-z tos] IPv4-mcast-group
  ping [-6AaDdfHnNoOquvyY] [-b bufsiz] [-c count] [-e gateway]
      [-I interface] [-i wait] [-k addrtype] [-l preload] [-m hoplimit]
      [-p pattern] [-P policy] [-S sourceaddr] [-s packetsize] [-t timeout]
      [-W waittime] [-z tclass] [IPv6-hops ...] IPv6-host