Switch to using AudioEncoderG722 instead of ACMG722

This change switches from the old codec wrapper ACMG722 to the new
AudioEncodeG722 wrapped in an ACMGenericCodecWrapper.

BUG=4228
COAUTHOR=kwiberg@webrtc.org
R=tina.legrand@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/39879004

git-svn-id: http://webrtc.googlecode.com/svn/trunk/webrtc@8330 4adac7df-926f-26a2-2b94-8c16560cd09d