Deleting all ACM1 files

ACM1 is deprecated and replaced by ACM2
(webrtc/modules/audio_coding/acm2/).

BUG=2996
R=turaj@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/18429005

git-svn-id: http://webrtc.googlecode.com/svn/trunk@6115 4adac7df-926f-26a2-2b94-8c16560cd09d