Simulcast support for iOS/Android.

Simulcast support for iOS SDK (webrtc-sdk#4)

Support for simulcast in Android SDK (webrtc-sdk#3)

include simulcast headers for mac also (webrtc-sdk#10)

Fix simulcast using hardware encoder on Android (webrtc-sdk#48)

Co-authored-by: Hiroshi Horie <548776+hiroshihorie@users.noreply.github.com>
Co-authored-by: Angelika Serwa <angelika.serwa@gmail.com>

sdk/objc/native/src/audio/audio_device_ios.mm

@@ -62,16 +62,6 @@
 const UInt16 kFixedPlayoutDelayEstimate = 30;
 const UInt16 kFixedRecordDelayEstimate = 30;
 
-enum AudioDeviceMessageType : uint32_t {
-  kMessageTypeInterruptionBegin,
-  kMessageTypeInterruptionEnd,
-  kMessageTypeValidRouteChange,
-  kMessageTypeCanPlayOrRecordChange,
-  kMessageTypePlayoutGlitchDetected,
-  kMessageOutputVolumeChange,
-  kMessageTypeAudioWillRecord,
-};
-
 using ios::CheckAndLogError;
 
 #if !defined(NDEBUG)