Add support for long options

[lholota]

Apparently options with long values can be split into multiple options and the value itself should be combined as specified in: https://tools.ietf.org/html/rfc3396

How it works

An option can be specified multiple times in the options buffer.

• If it is specified multiple times, the value must be concatenated.
• The option value should be concatenated in the same order it is present in the packet.

Note: This only applies to options which have a variable length