am afa583e6: SipAudioCall: expose startAudio()

Merge commit 'afa583e6557557577188c3e40146ac8d6f2aa7c7' into gingerbread-plus-aosp

* commit 'afa583e6557557577188c3e40146ac8d6f2aa7c7':
  SipAudioCall: expose startAudio()