casper/cap_net: Expose pack/unpack functions

[jfree]

Summary

Expose the interface to pack and unpack addrinfo and hostent structures.

This is useful in programs that pass these structures to/from a libcasper
process via nvlist

[jfree]

Bumping this

[markj]

I think this is ok, but I'd rather avoid it if possible. That is, I hope we can avoid having to serialize addrinfo structures in syslogd.

[markj]

In D41402#1070519, @markj wrote:

I think this is ok, but I'd rather avoid it if possible. That is, I hope we can avoid having to serialize addrinfo structures in syslogd.

I believe this patch is no longer needed after D47104?