r6138 (https://webrtc-codereview.appspot.com/18399005/) somewhat ill-advisedly removed the saturation step at the end of aec_core.c:NonLinearProcessing(); this patch restores it. BUG= R=andrew@webrtc.org, bjornv@webrtc.org Review URL: https://webrtc-codereview.appspot.com/18479004 git-svn-id: http://webrtc.googlecode.com/svn/trunk@6263 4adac7df-926f-26a2-2b94-8c16560cd09d