stagefright: Pass AAC profile from MatroskaExtractor

 * Needed by framework to determine audio apth

Change-Id: I8d928852fb4a24e3d575d70fbf366bae1a178b31
stagefright: Cleanup and improve format parsing

 * Move FFMPEG-specific exceptions to FFMPEGSoftCodec
 * Add handling for AAC MAIN profile
 * Use the new OMX_AUDIO_CodingAndroidAC3 to handle AC3

Change-Id: Ibb806cd2b9dd23dc1e1b2c862fcde40605023a49