QBindableInterface iface 声明为 constexpr 导致 QBindable 构造错误

引发错误的代码：

```

#include <QObject>
#include <QBindable>
#include <QProperty>
#include <QDebug>

class Foo : public QObject
{
    Q_OBJECT
    Q_PROPERTY(int myVal READ myVal WRITE setMyVal NOTIFY myValChanged CONSTANT)
public:
    explicit Foo():m_myVal(5){}
    int myVal() const { return m_myVal; }
    void setMyVal(int newvalue)

{         if(m_myVal == newvalue) return;         m_myVal = newvalue;         emit myValChanged(newvalue);     }

signals:
    void myValChanged(int newVal);

private:
    int m_myVal;
};

int main()

{     Foo myfoo;     QBindable<int> obj(&myfoo, "myVal");     QProperty<int> prop([&]()\{return obj.value();}

);
    auto change = prop.onValueChanged([&](){qDebug() << "value changed:" << prop.value();});
    myfoo.setMyVal(10); 

    return 0;
}

#include "main.moc"

```

编译上述代码时出现如下错误：

 error: constexpr variable 'iface<int>' must be initialized by a constant expression

 

解决办法：修改 qproperty.h 文件  667 行 代码 `inline constexpr QBindableInterface iface = {`为`inline QBindableInterface iface = {`