[gnome-desktop] (22 commits) ...ci: Do not build GTK4 libraries on fedora:34

[Emmanuele Bassi <ebassi src gnome org>]

Summary of changes:

  7f1c365... Drop unnecessary include (*)
  cf27647... Replace deprecated use of GTimeVal (*)
  a2a5b10... build: Quiet the introspection scanner (*)
  3a6d839... build: Require a more recent version of Meson (*)
  2fa71b1... build: Use non-deprecated methods (*)
  931cc88... Remove use of GTimeVal (*)
  fc410c0... Avoid using deprecated GLib API (*)
  935ee8d... Remove unnecessary include to GDK (*)
  056aa4e... build: Use idiomatic Meson (*)
  81e5d43... tests: Ignore deprecated API (*)
  7067fc5... Remove invalid gtk-doc marker (*)
  760a975... Add libgnome-desktop-4 (*)
  b57f269... build: Rename gtk_dep to gtk3_dep (*)
  7c51cdc... Use the C type for the element-type annotation (*)
  b8464ec... Add libgnome-desktop-ui-4 (*)
  bd7426d... Remove unused GnomeRRScreenPrivate field (*)
  7c95b7b... build: Split libgnome-desktop-ui-4 into two (*)
  c2c7414... Port gnome-bg and gnome-rr to GTK4 (*)
  5ea55a8... Enable optional building of GTK4 libraries (*)
  3fedfab... build: Allow disabling the legacy libgnome-desktop-3.0 (*)
  ead99fd... build: Add configuration summary (*)
  64b0e55... ci: Do not build GTK4 libraries on fedora:34 (*)

(*) This commit already existed in another branch; no separate mail sent