Log Message:
Update gnome-desktop3 to 3.20.1

- Add a way to get the frequency for a mode as a floating number
- Reduce log spam in thumbnailing
- Capitalize language and territory names
- Add default keyboard layout for Mexico and Guatemala
- Avoid a crash when thumbnailing
- Be more careful when parsing locales
- Fix a compiler warning in gnome-rr
- Fix turning off tiled monitors
- Fix thumbnailing of animations
- Support g_autoptr() for all libgnome-desktop object types
- Remove unused EDID parsing code
- Support underscanning
- Export dpms information
- Add support for tiled monitors
- Fix build of installed-tests
- Add support for overscan compensation in displays (#748560)
- Translation updates