Support of DHCP Option 61

The TCP/IP stack shall be extended to support DHCP Option 61. Option 61, namely "Client-Identifier", can be used by DHCP servers to index their database of address bindings.

Possible use case: Assign IP address by device's client identifier
Instead of using the device's MAC address, the DHCP server provides an IP address to the requesting device on the basis of the device's Option 61 value, which by definition must be uinque for all clients in an administrative domain.This can make the exchange of devices in the network very easy, since there is no need to reconfigured the DHCP server's MAC address configuration.

The definition of Option 61 can be found here: https://www.ietf.org/rfc/rfc2132.txt 

   Code   Len   Type  Client-Identifier
   +-----+-----+-----+-----+-----+---
   |  61 |  n  |  t1 |  i1 |  i2 | ...
   +-----+-----+-----+-----+-----+---

API Information

1. The Option must be applied before a "Set config" has been send to the TCP/IP set.