Fix display of option pages

Improve handling of page sizes, especially of the kits page (with
small and big dialog sizes).

Change-Id: I8dba7b4b5028cb41e0719a2f9aec15eb89858a8a
Reviewed-by: Tim Jenssen <tim.jenssen@theqtcompany.com>

src/plugins/coreplugin/dialogs/settingsdialog.cpp

@@ -337,6 +337,7 @@ public:
     {
         setFrameStyle(QFrame::NoFrame | QFrame::Plain);
         viewport()->setAutoFillBackground(false);
+        setWidgetResizable(true);
     }
 private:
     void resizeEvent(QResizeEvent *event) override
@@ -385,7 +386,6 @@ private:
             return 0;
         return list.first()->sizeHint().width();
     }
-
 };