Replace the QMatrix4x4_Accessor hack in qsgbatchrenderer

struct QMatrix4x4_Accessor
{
    float m[4][4];
    int flagBits;

    static bool isTranslate(const QMatrix4x4 &m) { return ((const QMatrix4x4_Accessor &) m).flagBits <= 0x1; }
    static bool isScale(const QMatrix4x4 &m) { return ((const QMatrix4x4_Accessor &) m).flagBits <= 0x2; }
    static bool is2DSafe(const QMatrix4x4 &m) { return ((const QMatrix4x4_Accessor &) m).flagBits < 0x8; }
};