Fix licensing issues (#5786)

* Fix GPL address (#5772)

* Replace showcase icons with Open Iconic

- The icon set Open Iconic is licensed under MIT unlike the previous
  ones, which are CC-BY-NC

examples/demo/showcase/data/icons/README

@@ -1 +1,4 @@
-Icon from http://www.gentleface.com/free_icon_set.html#geticons
+Icons adapted from the Open Iconic set of icons, which are licensed under MIT.
+
+https://useiconic.com/
+https://github.com/iconic/open-iconic

examples/demo/showcase/showcase.kv

@@ -65,16 +65,16 @@ BoxLayout:
                     app.go_screen(idx)
             ActionToggleButton:
                 text: 'Toggle sourcecode'
-                icon: 'data/icons/sourcecode.png'
+                icon: 'data/icons/bug.png'
                 on_release: app.toggle_source_code()
             ActionButton:
                 text: 'Previous screen'
-                icon: 'data/icons/prev.png'
+                icon: 'data/icons/chevron-left.png'
                 on_release: app.go_previous_screen()
 
             ActionButton:
                 text: 'Next screen'
-                icon: 'data/icons/next.png'
+                icon: 'data/icons/chevron-right.png'
                 on_release: app.go_next_screen()
                 important: True
 

kivy/tools/highlight/kivy-mode.el

@@ -20,7 +20,7 @@
 
 ;; You should have received a copy of the GNU General Public License along
 ;; with GNU Emacs; see the file COPYING. If not, write to the Free Software
-;; Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
+;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301,
 ;; USA.
 
 ;;; Installation: