Fix unused private field warning in QMacMime.

Does not apply to Qt 5.

Change-Id: Ia1e5c5d8813a2285dd80189f7264d959ea8056c1
Reviewed-by: David Faure (KDE) <faure@kde.org>
Update for OS X Mavericks.

(Qt 4 equivalent of qtbase/bd97768ae54d643270e824f74d152892dbea1b9f)

Change-Id: I7ecebd2e185d61a0baeb5b47b802c2f760edeff3
Reviewed-by: Gabriel de Dietrich <gabriel.dedietrich@digia.com>