gtk-engine*: relocate under development/libraries

pkgs/top-level/all-packages.nix

@@ -11585,6 +11585,12 @@ in
   gtkmm2 = callPackage ../development/libraries/gtkmm/2.x.nix { };
   gtkmm3 = callPackage ../development/libraries/gtkmm/3.x.nix { };
 
+  gtk_engines = callPackage ../development/libraries/gtk-engines { };
+
+  gtk-engine-bluecurve = callPackage ../development/libraries/gtk-engine-bluecurve { };
+
+  gtk-engine-murrine = callPackage ../development/libraries/gtk-engine-murrine { };
+
   gtk-sharp-2_0 = callPackage ../development/libraries/gtk-sharp/2.0.nix {
     inherit (gnome2) libglade libgtkhtml gtkhtml
               libgnomecanvas libgnomeui libgnomeprint
@@ -23400,12 +23406,6 @@ in
 
   latte-dock = libsForQt5.callPackage ../applications/misc/latte-dock { };
 
-  gtk_engines = callPackage ../misc/themes/gtk2/gtk-engines { };
-
-  gtk-engine-bluecurve = callPackage ../misc/themes/gtk2/gtk-engine-bluecurve { };
-
-  gtk-engine-murrine = callPackage ../misc/themes/gtk2/gtk-engine-murrine { };
-
   gnome-themes-extra = gnome3.gnome-themes-extra;
 
   rox-filer = callPackage ../desktops/rox/rox-filer {