Increase size of statistics buffer

#ifdef FAST_MIXER_STATISTICS

    // Recently collected samples of per-cycle monotonic time, thread CPU time, and CPU frequency.

    // kSamplingN is the size of the sampling frame, and must be a power of 2 <= 0x8000.

    static const uint32_t kSamplingN = 0x1000;

    static const uint32_t kSamplingN = 0x8000;

    // The bounds define the interval of valid samples, and are represented as follows:

    //      newest open (excluded) endpoint   = lower 16 bits of bounds, modulo N

    //      oldest closed (included) endpoint = upper 16 bits of bounds, modulo N