[REG 5.3->5.4] BC break in qvariant.h due to MSVC name mangling?

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qtbug41810.exe - Entry Point Not Found
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The procedure entry point ?convert@QVariant@@QEBA_NHPEAX@Z could not be located in the dynamic link library d:\dev\projects\qtbug41810_53\debug\qtbug41810.exe. 

#ifndef Q_NO_TEMPLATE_FRIENDS
    template<typename T>
    friend inline T qvariant_cast(const QVariant &);
    template<typename T> friend struct QtPrivate::QVariantValueHelper;
protected:
#else
public:
#endif
    Private d;
    void create(int type, const void *copy);
    bool cmp(const QVariant &other) const;
    int compare(const QVariant &other) const;
    bool convert(const int t, void *ptr) const;