Make equality operators in QtNetwork value types hidden friends

[build] /Users/vohi/qt/dev/build/qtbase/include/QtNetwork/../../../../qtbase/src/network/kernel/qhostaddress.h:158:13: note: candidate function not viable: no known conversion from 'A' to 'QHostAddress::SpecialAddress' for 1st argument
[build] inline bool operator ==(QHostAddress::SpecialAddress address1, const QHostAddress &address2)
[build]             ^
[build] /Users/vohi/qt/dev/build/qtbase/include/QtNetwork/../../../../qtbase/src/network/access/qhstspolicy.h:92:23: note: candidate function not viable: no known conversion from 'A' to 'const QHstsPolicy' for 1st argument
[build] Q_NETWORK_EXPORT bool operator==(const QHstsPolicy &lhs, const QHstsPolicy &rhs);
[build]                       ^
[build] /Users/vohi/qt/dev/build/qtbase/include/QtNetwork/../../../../qtbase/src/network/access/qhttp2configuration.h:91:23: note: candidate function not viable: no known conversion from 'A' to 'const QHttp2Configuration' for 1st argument
[build] Q_NETWORK_EXPORT bool operator==(const QHttp2Configuration &lhs, const QHttp2Configuration &rhs);
[build]                       ^
[build] /Users/vohi/qt/dev/build/qtbase/include/QtNetwork/../../../../qtbase/src/network/ssl/qssldiffiehellmanparameters.h:66:23: note: candidate function not viable: no known conversion from 'A' to 'const QSslDiffieHellmanParameters' for 1st argument
[build] Q_NETWORK_EXPORT bool operator==(const QSslDiffieHellmanParameters &lhs, const QSslDiffieHellmanParameters &rhs) noexcept;
[build]                       ^
[build] /Users/vohi/qt/dev/build/qtbase/include/QtNetwork/../../../../qtbase/src/network/ssl/qsslellipticcurve.h:90:23: note: candidate function not viable: no known conversion from 'A' to 'QSslEllipticCurve' for 1st argument
[build] constexpr inline bool operator==(QSslEllipticCurve lhs, QSslEllipticCurve rhs) noexcept