webrtc echo canceller update v3

[arun@xxxxxxxxxxxx (arun@xxxxxxxxxxxx)]

from v1:
Patch 1-3: Update code for the changed API and use some new features
Patch 4-7: Add support for multi-channel AEC
Patch 8,9: Misc. changes, hook up some tracing support
Patch 10,11: Fix up AGC after the update

in v2:
Patch 12: Bug fix on the previous series
Patch 13-17: Make more stuff tunable as modargs
Patch 18-20: Minor fixes
Patch 21-24: Add beamforing support
Patch 25: Trivial header update

in v3:
Squashed a couple of fixes related that could be, removed pa_prefix from
private functions