Adjust width of SelectProductDialog's side panel according to its contents.

The width is determined at runtime based on the largest page in the
QTabWidget.  Without this fix, the side panel would annoyingly change
width as you selected the search tab for the first time -- this was
particularly annoying in the de_DE locale.

glabels/CMakeLists.txt

@@ -24,6 +24,7 @@ set (glabels_sources
   MainWindow.cpp
   MergeView.cpp
   MiniPreviewPixmap.cpp
+  NotebookUtil.cpp
   ObjectEditor.cpp
   PreferencesDialog.cpp
   PrintView.cpp