Import dhcpcd-6.3.2 with the following changes:

  * Improvements to autoconf build emulation
  * CARRIER/NOCARRIER are now run outside of the IPv4 runs
  * validate domains correctly which contain a - on non bash shells
  * don't remove IPv6 addresses from internal state when added as tentative
  * HUP now rebinds, ALRM now releases - the -x and -k flags work as
    they used to
  * Add -M, --master option to force dhcpcd into master mode even if one
    interface is specified on the command line
  * Fix a crash when receiving a reconfigure key
  * Dumping a DHCPv4 lease works again
  * SEND_DAD code removed
  * hoplimit is no longer defined for DHCPv6 messages
  * hoplimit of 255 for IPv6 RS/ND message is now defined at the socket
    instead of ancillary data with the message