[RFC][VOTE] Warn about invalid strings in arithmetic

Good evening, Just over two weeks ago I introduced this RFC. There's not been a lot of discussion since then, and there's no unfinished business that I can think of. So, I think it's time to put it to a vote: https://wiki.php.net/rfc/invalid_strings_in_arithmetic Voting starts today (2016-01-23) and will end next Sunday (2016-01-31), an 8-day period, which means there's half of this weekend and all of next, more than enough time I hope. Thanks.