Extend netstat to display the TCP congestion control

[tuexen]

Summary

This patch adds the -c option to netstat, which enables the displaying of the name of the congestion control module used by a TCP connection.

This depends on D26412.

[jilles]

Perhaps it is better to match sockstat (D26413) and make the option -C instead of -c.

[tuexen]

Use -C instead of -c.

[tuexen]

In D26414#587458, @jilles wrote:

Perhaps it is better to match sockstat (D26413) and make the option -C instead of -c.

Done, but the options are already not in sync:

• -p in netstat and -P in sockstat for selecting the protocol.
• -a in netstat and -l in sockstat for showing listening sockets.

[rscheff]

I wanted to suggest using -C (for reasons, instead of -c), but seeing this is already addressed...