Import dhcpcd-6.2.0 with the following changes:

* Fix NAK backoff when a server NAKs a REQUEST after a DISCOVER.
* Fix IPv6 ICMP filtering on Android (RS/RA now works)
* Fix sending of DHCPv6 FQDN when only hostname specified
* Add support for RFC3925 Vendor-Identifying Vendor Options
* Remove hard coded DHCP/DHCPv6 options and embed dhcpcd-definitions.conf.
  This actually results in a slightly smaller binary than before and has the added advantage that the option definitions are now all held within one file.
* Change IAID to default from the last 4 bytes of the MAC address.
  Rationale in the commit, but in a nutshell it allows for a stable IAID between reboots without persistent storage and across different OS's who name or number it differently to each other.
* RFC4242, Information Refresh Time Option for DHCPv6.
* Fix processing of inet4 addr in vendor options and terminate correctly.
* Preserve vendor encapsulated options.
* Fix renewal of Prefix Delegation. Only spam the log if a lease has a new address or changes the vltime of an existing address.
* Add noipv4 and noipv6 options.
* Warn about missing interfaces which require prefix delegation.
* If we timeout, remove any waitip config so that we daemonise correctly.
* Remove the IPv6 forwarding router check as valid use cases exist where you would want IPv6 RS/RA on a router.
* Pass the correct run directory to dhcpcd-run-hooks