Implementation if mono-to-stereo and vice versa in ACM.

Added stereo-to-mono and mono-to-stereo tests to end of TestStereo.cpp.

BUG=Aim to resolve issue 207, "Investigate stereo capture handling in modules"
TEST=audio_coding_module_test

Review URL: http://webrtc-codereview.appspot.com/345002

git-svn-id: http://webrtc.googlecode.com/svn/trunk@1385 4adac7df-926f-26a2-2b94-8c16560cd09d
4 files changed