gtk3: updated to 3.24.24

Overview of Changes in GTK+ 3.24.24
===================================

* GtkColorChooser:
- Update the default color palette

* GtkFontChooser:
- Fix family-only mode to return regular style

* GtkTreeView:
- Don't set focus-on-click for header buttons

* Accessibility:
- Implement scrollSubstringTo
- Add a11y support to GtkPlug/GtkSocket

* Printing:
- Allow the lpr backend to print pdf and ps files

* Theme:
- Update gesture graphics
- Update HighContrast css

* Wayland:
- Support the primary-selection-unstable-v1 protocol

* X11:
- Fix a crash with parent-relative backgrounds

* Broadway:
- Set modifier state of scroll events

* Build:
- Fix pc file generation on NixOS

* OS X:
- Restore command-key bindings

* Windows:
- Fix meson build with epoxy subproject

* Translation updates:
Basque
Brazilian Portuguese
British English
Catalan
Croatian
Czech
French
Galician
German
Greek
Hebrew
Hungarian
Indonesian
Italian
Kazakh
Latvian
Lithuanian
Persian
Polish
Portuguese
Slovak
Slovenian
Spanish
Swedish
Turkish
Ukrainian

(adam)