Alt Hold issues in Copter 4.0

@rmackay9 @Leonardthall Dear Developers could you give some information about rangefinders implementation in Arducopter 4 ? I hope there will be changes in code from 4.04 which will improve ALT HOLD with rangefinders and disable aggressive terrain follow (bushes, trees, reeds follow):
https://discuss.ardupilot.org/t/incorrect-alt-hold-when-rangefinder-is-installed-and-used/56151/6