distinguish ICMP and ICMP6 in error messages

[auerswal]

This is a suggestion to differentiate between some IPv4 and IPv6 socket related error messages.

1. After a failed attempt to get the protocol ipv6-icmp I think it would be better to say that this protocol could not be resolved instead of using just the name icmp in the error message.

   $ getent protocols icmp
   icmp                  1 ICMP
   $ getent protocols ipv6-icmp
   ipv6-icmp             58 IPv6-ICMP
   

2. When setting the source IPv6 address of an AF_ICMP6 socket fails use ICMP6 instead of ICMP in the error message.

This might help the user to start looking for IPv6 issues, or tying to find out why IPv6 is used in the first place. When the error messages look identically for both IPv4 and IPv6 the user might not even realize that the problem is related to IPv6 or even that IPv6 is in use at all.

Please let me know what you think.

[coveralls]

Coverage decreased (-0.4%) to 79.289% when pulling d6c6837c38d9d9dc98c04e67acca3fbacaab706d on auerswal:v6_vs_v4 into 87c9b29d865a893d0e3dfadd7bbd8f4affdbc9e4 on schweikert:develop.

[auerswal]

Is there any interest in this work?

[auerswal]

Closing this pull request due to lack of interest in this work.