gnu: Add adwaita-icon-theme.

* gnu/packages/gnome.scm (adwaita-icon-theme): New variable.

gnu/packages/gnome.scm

@@ -393,6 +393,20 @@ update-desktop-database: updates the database containing a cache of MIME types
      "Icons for the GNOME desktop.")
     (license license:lgpl3))) ; or Creative Commons BY-SA 3.0
 
+;; gnome-icon-theme was renamed to adwaita-icon-theme after version 3.12.0.
+(define-public adwaita-icon-theme
+  (package (inherit gnome-icon-theme)
+    (name "adwaita-icon-theme")
+    (version "3.16.2")
+    (source (origin
+              (method url-fetch)
+              (uri (string-append "mirror://gnome/sources/" name "/"
+                                  (version-major+minor version) "/"
+                                  name "-" version ".tar.xz"))
+              (sha256
+               (base32
+                "1hmlw7kvhr7c2asc5y77adpymi9ka17gaf76zz835nwwffnn4rlw"))))))
+
 (define-public shared-mime-info
   (package
     (name "shared-mime-info")