Add RingCount for sexpots manual answer.

Was discussed in irc but want to make it official. Even though I'm using s0=3, the modem never answers when receiving from my UK number for some reason. So, I'm asking that we have the ability to have an "answer after x rings" ability.

Currently, if using manual, sexpots answers after the first ring so it wont pick up any caller ID information. I need one modem to answer after 2 and one after 3 rings since one of my providers will ring both lines, so I can't have both modems answer at once.

This should be a trivial addition, I hope, but without it, I can't get caller ID on my UK number since I must use manual answer.