Do not use QAbstractItemModel::reset().

Change-Id: Ie49bdf576a6d3543aef6df133b27c8827775c935
Rationale:
    a) It is conceptually cleaner to do the changes to the model
       in between calls to beginResetModel() and endResetModel,
       respectively.
    b) The function is deprecated in Qt 5, for exactly that reason.
Reviewed-by: hjk <qthjk@ovi.com>

src/plugins/coreplugin/dialogs/settingsdialog.cpp

@@ -137,6 +137,8 @@ QVariant CategoryModel::data(const QModelIndex &index, int role) const
 void CategoryModel::setPages(const QList<IOptionsPage*> &pages,
                              const QList<IOptionsPageProvider *> &providers)
 {
+    beginResetModel();
+
     // Clear any previous categories
     qDeleteAll(m_categories);
     m_categories.clear();
@@ -176,7 +178,7 @@ void CategoryModel::setPages(const QList<IOptionsPage*> &pages,
         category->providers.append(provider);
     }
 
-    reset();
+    endResetModel();
 }
 
 Category *CategoryModel::findCategoryById(const QString &id)