NetEq4: Removing templatization for AudioMultiVector

This saves approx 6% runtime for neteq4_speed_test.
$ time out/Release/neteq4_speed_test --runtime_ms=50000000

BUG=1363
R=minyue@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/2320006

git-svn-id: http://webrtc.googlecode.com/svn/trunk/webrtc@4885 4adac7df-926f-26a2-2b94-8c16560cd09d
31 files changed