Update ICMP Spec with additions from RFC 1122/950

[rssen]

RFC 950

• adds a new Message Type: Address Mask Request/Reply with Code 17,18 (p. 10)
• Wikipedia

RFC 1122 Defines additional codes for:

• ICMP Destination Unreachable (p. 39)

The following additional codes [for Destination Unreachable] are hereby defined:
   6 = destination network unknown
   7 = destination host unknown
   8 = source host isolated
   9 = communication with destination network administratively prohibited
   10 = communication with destination host administratively prohibited
   11 = network unreachable for type of service
   12 = host unreachable for type of service

• ICMP Parameter Problem (p. 42)

A new variant on the Parameter Problem message is hereby defined:
   Code 1 = required option is missing.

[senier]

This is a new feature which should not delay 0.4.1 further.

[treiher]

Moved to Componolit/RecordFlux-specifications#1.