Mark as unused the private members that aren't and CANNOT be used

Those members were left uninitialised by inline constructors and/or
the destructor of those classes is/was also inline. Those members
cannot be used to store pointers that need managing during the Qt 5.x
lifetime.

They can be used to store simple values, as if they were integers.

Detected by Apple Clang 4.2.

Change-Id: I20e2def7c4006668e2d6a7e332c89e2dc8c2a184
Reviewed-by: Konstantin Ritt <ritt.ks@gmail.com>
Reviewed-by: Lars Knoll <lars.knoll@digia.com>

src/dbus/qdbuserror.cpp

@@ -257,7 +257,9 @@ static inline QDBusError::ErrorType get(const char *name)
 QDBusError::QDBusError()
     : code(NoError)
 {
-
+    // ### This class has an implicit (therefore inline) destructor
+    // so the following field cannot be used.
+    Q_UNUSED(unused);
 }
 
 #ifndef QT_BOOTSTRAPPED

src/xml/sax/qxml.cpp

@@ -985,12 +985,22 @@ void QXmlNamespaceSupport::reset()
 
     Constructs an empty attribute list.
 */
+QXmlAttributes::QXmlAttributes()
+{
+    // ### In Qt 5.0, this function was inlined and d was not initialized
+    // The member cannot be used until Qt 6.0
+    Q_UNUSED(d);
+}
 
 /*!
     \fn QXmlAttributes::~QXmlAttributes()
 
     Destroys the attributes object.
 */
+QXmlAttributes::~QXmlAttributes()
+{
+}
+
 
 /*!
     Looks up the index of an attribute by the qualified name \a qName.
@@ -2400,11 +2410,21 @@ events are reported.
 
     Constructs a handler for use with subclasses of QXmlReader.
 */
+QXmlDefaultHandler::QXmlDefaultHandler()
+{
+    // ### In Qt 5.0, this function was inlined and d was not initialized
+    // The member cannot be used until Qt 6.0
+    Q_UNUSED(d);
+}
+
 /*!
     \fn QXmlDefaultHandler::~QXmlDefaultHandler()
 
     Destroys the handler.
 */
+QXmlDefaultHandler::~QXmlDefaultHandler()
+{
+}
 
 /*!
     \reimp

src/xml/sax/qxml.h

@@ -117,8 +117,8 @@ private:
 class Q_XML_EXPORT QXmlAttributes
 {
 public:
-    QXmlAttributes() {}
-    virtual ~QXmlAttributes() {}
+    QXmlAttributes();
+    virtual ~QXmlAttributes();
 
     int index(const QString& qName) const;
     int index(QLatin1String qName) const;
@@ -365,8 +365,8 @@ public:
 class Q_XML_EXPORT QXmlDefaultHandler : public QXmlContentHandler, public QXmlErrorHandler, public QXmlDTDHandler, public QXmlEntityResolver, public QXmlLexicalHandler, public QXmlDeclHandler
 {
 public:
-    QXmlDefaultHandler() { }
-    virtual ~QXmlDefaultHandler() { }
+    QXmlDefaultHandler();
+    virtual ~QXmlDefaultHandler();
 
     void setDocumentLocator(QXmlLocator* locator);
     bool startDocument();