Method setHead

src/fl/stl/circular_buffer.h:145–145

    fl::size tail() const { return mTail; }
    bool isFull() const { return mFull; }
    void setHead(fl::size h) { mHead = h; }
    void setTail(fl::size t) { mTail = t; }
    void setFull(bool f) { mFull = f; }