Fix font rendering gamma correction on Mac

It needs a 2.0 gamma (as in Qt 4) in platform plugin styleHint.

Change-Id: I2286532c607554c41baee4fa348cd7899bf010e1
Reviewed-by: Morten Johan Sørvig <morten.sorvig@nokia.com>

src/plugins/platforms/cocoa/qcocoaintegration.h

@@ -101,6 +101,7 @@ public:
     QStringList themeNames() const;
     QPlatformTheme *createPlatformTheme(const QString &name) const;
     QPlatformServices *services() const;
+    QVariant styleHint(StyleHint hint) const;
 
 private:
 

src/plugins/platforms/cocoa/qcocoaintegration.mm

@@ -245,4 +245,11 @@ QPlatformServices *QCocoaIntegration::services() const
     return mServices.data();
 }
 
+QVariant QCocoaIntegration::styleHint(StyleHint hint) const
+{
+    if (hint == QPlatformIntegration::FontSmoothingGamma)
+        return 2.0;
+    return QPlatformIntegration::styleHint(hint);
+}
+
 QT_END_NAMESPACE