Regularly dump TCP_INFO statistics of outgoing connections

Backport from PR #401 to 1.7.

(cherry picked from commit b88bd91447cb143ae5a6a08ca54a9d5166314d6e)

Conflicts:
	src/libcutil.clib

Closes #401
Maybe I'm missing something, but what exactly is `_my_threads` good for?
Also I expected `Lwt.ignore_result (run_report _connections)` ... but I suppose you tested this and it's running that thread?