glib.py: Fix Python 3 TypeError in gdb pretty-printers

https://bugzilla.gnome.org/show_bug.cgi?id=749092

glib/glib.py

@@ -67,6 +67,8 @@ class GListPrinter:
             self.count = self.count + 1
             return ('[%d]' % count, data)
 
+        __next__ = next
+
     def __init__ (self, val, listtype):
         self.val = val
         self.listtype = listtype
@@ -121,6 +123,8 @@ class GHashPrinter:
                     return ('[%dk]'% (self.pos), key)
             raise StopIteration
 
+        __next__ = next
+
     def __init__ (self, val):
         self.val = val
         self.keys_are_strings = False