Clean up AudioProcessing defaults and errors.

- Remove unneeded #defines and switch the remainder to consts.
- All AudioProcessing components are disabled by default, so remove
explicit disables.
- AudioProcessing uses a rational 16 kHz mono default, so no need to
explictly initialize.
- Add assert(false) to real-time errors which should not occur.

TESTED=trybots
R=bjornv@webrtc.org, xians@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/2253005

git-svn-id: http://webrtc.googlecode.com/svn/trunk/webrtc@4924 4adac7df-926f-26a2-2b94-8c16560cd09d
4 files changed