Log Message:
Import dhcpcd-7.0.8 with the following changes:
  *  Don't use IP_PKTINFO on NetBSD-7 as it's incomplete.
  *  Workaround RTM_NEWADDR sending the wrong broadcast address
     on NetBSD-7.
  *  Silence diagnostics if an address vanishes when reading
     it's flags on all BSD's.
  *  Misc compiler warnings fixed.