Import GDK in preparation for GTK3 conversion

Some parts of GTK moved to GDK, so we need to import the latter for things to
work after the conversion script runs.

Signed-off-by: Sascha Silbe <silbe@activitycentral.com>

src/sugar3/activity/widgets.py

@@ -15,6 +15,7 @@
 # Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 # Boston, MA 02111-1307, USA.
 
+from gtk import gdk
 import gtk
 import gettext
 import gconf

src/sugar3/graphics/palettewindow.py

@@ -23,6 +23,7 @@ STABLE.
 
 import logging
 
+from gtk import gdk
 import gtk
 import gobject
 

src/sugar3/graphics/style.py

@@ -25,6 +25,7 @@ STABLE.
 import os
 import logging
 
+from gtk import gdk
 import gtk
 import pango
 import gconf

src/sugar3/graphics/window.py

@@ -21,6 +21,7 @@ STABLE.
 """
 
 import gobject
+from gtk import gdk
 import gtk
 import warnings
 

src/sugar3/wm.py

@@ -20,6 +20,7 @@ UNSTABLE. Used only internally by Activity and jarabe.
 """
 
 import gtk
+from gtk import gdk
 import logging