MFC r223788, r223790, r223824 236808

MFC r223788, r223790, r223824 236808

Merge netflow v9 support (user side)

r223788 -  Rewrite the flowctl utility to add it support for displaying both IPv4 and IPv4 flows.
r223790 -  Update manual page. Mention IPv6 support, ..
r223824 - Conditionally compile in the IPv4/IPv6 address family support.
r236808 - Add "human" option to print IPv4/IPv6 flows in human-readable format.

Additionally, implement compatibility code for syntax changes introduced in r223788.
Flowctl supports specifying node both as absolute path (new style) and as node
name without colon (old style).

No objection from:  glebius
Approved by:        ae(mentor)

git-svn-id: svn://svn.freebsd.org/base/stable/8@238620 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f