4.10.0: (stable)

There are no releases between 4.0.x and 4.10.0. This release is
called 4.10.0 because the tutorial describes the new API in gtkmm 4.10.0
and some of the example programs use this new API. Other example programs
use API which is now deprecated. It's not possible to build all examples
with warnings=fatal.

* Add the "Deprecations in gtkmm 4.10" section
* Update the Dialogs chapter
* Add "The DropDown Widget" chapter
* Add the "ListView, GridView, ColumnView" chapter
  (Kjell Ahlstedt)
* String fixes
  (Anders Jonsson) Merge request !17

Example programs:
* Update the others/window example
* others: Remove arrow, cellrenderercustom, treemodelcustom,
  idle, statusbar
* book/buildapp: Don't use deprecated API
* book/headerbar: Use AlertDialog instead of MessageDialog
* book/recent_files: Use FileDialog instead of FileChooserDialog
* Printing examples: Don't use deprecated API
* Replace the IconView example by a GridView example
* Replace most Dialog examples: messagedialog -> alertdialog,
  colorchooserdialog -> colordialog, filechooserdialog -> filedialog,
  fontchooserdialog -> fontdialog, simple -> windowdialog
* Use Gtk::Window instead of Gtk::Dialog in book/builder/basic,
  book/builder/derived, book/scrolledwindow
* Infobar example: Don't use deprecated Gtk::InfoBar
*  Add 4 DropDown examples
* Custom CSS Names: Show custom CSS class
* Remove the buttons/volumebutton example
* Add 5 ColumnView and 2 ListView examples in book/listmodelviews
  (Kjell Ahlstedt)

Build:
* Require gtkmm-4.0 >= 4.10.0
* Set warnings=max when testing a dist tarball
  (Kjell Ahlstedt)