Add TRACK_FAST for IAudioFlinger::createTrack

    // or-able bits shared by createTrack and openRecord, but not all combinations make sense

    enum {

        TRACK_DEFAULT = 0,

        TRACK_TIMED   = 1,

        TRACK_DEFAULT = 0,  // client requests a default AudioTrack

        TRACK_TIMED   = 1,  // client requests a TimedAudioTrack

        TRACK_FAST    = 2,  // client requests a fast AudioTrack

    };

    typedef uint32_t track_flags_t;