Add test to verify that nested functions with free variables don't

cause the free variables to leak.

Lib/test/output/test_scope

@@ -14,3 +14,4 @@ test_scope
 13. UnboundLocal
 14. complex definitions
 15. scope of global statements
+16. check leaks

Lib/test/test_scope.py

@@ -383,3 +383,26 @@ def f():
     return g()
 verify(f() == 2)
 verify(x == 2)
+
+print "16. check leaks"
+
+class Foo:
+    count = 0
+    
+    def __init__(self):
+        Foo.count += 1
+
+    def __del__(self):
+        Foo.count -= 1
+
+def f1():
+    x = Foo()
+    def f2():
+        return x
+    f2()
+    
+for i in range(100):
+    f1()
+
+verify(Foo.count == 0)
+