Try to make gobject.py work with both pythons

This change was suggested on the fedora test list, and has been
reported to work.

gobject/gobject.py

@@ -238,7 +238,7 @@ class GFrameDecorator:
                 return i
         return -1
 
-    def __next__ (self):
+    def next (self):
         # Ensure we have enough frames for a full signal emission
         self.fill()
 
@@ -274,6 +274,9 @@ class GFrameDecorator:
 
         return self.queue.pop(0)
 
+    def __next__ (self):
+        return self.next()
+
 class GFrameFilter(object):
     name = 'glib'
     enabled = True