- (offset - 4) explained better
 - Modified Dhcpv6Srv::unpackOptions()
 - setHWAddrMember() mac_addr renamed (this time for real)
 - Commented out unused variables
 - RelayInfo now uses DEFAULT_ADDRESS6 in ctor
 - LibDHCP::unpackOptions6 and callback now used uniformly
 - Clarified that ERO is Echo Request Option (RFC4994)
 - unpackOptions4 in libdhcp and Dhcp4Srv no longer throw when
   truncated option is received.