Fix clang style warnings in webrtc/modules/audio_coding/neteq

Mostly this consists of marking functions with override when
applicable, and moving function bodies from .h to .cc files.

BUG=163
R=henrik.lundin@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/44109004

Cr-Original-Commit-Position: refs/heads/master@{#8960}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 7f6c4d42a2605d1da39af3f957a46cf57b043b84
30 files changed