The first reconnection attempt waits for 1min, the second the 2min,
and so on up to 10min. There's a 1min jitter so that multiple failed
connections don't try to reconnect at the exact same time.
Closes: https://todo.sr.ht/~emersion/soju/161
git-svn-id: file:///srv/svn/repo/suika/trunk@735 f0ae65fe-ee39-954e-97ec-027ff2717ef4
