* src/dhcp_prot.c: Updated set_fixed_tag(), set_variable_tag(), and unset_tag() to handle TAG_PAD bytes properly. Also updated set_fixed_tag() and set_variable_tag() to permit setting options that already exist, but are a different size, rather than asserting. This corrects problems interacting with mis-behaving DHCP servers that reply with modified versions of a DHCP option sent by the eCos client, such as TAG_HOST_NAME.