Add global statements even for read of globals

test/simple_source/stmts/10_del.py

@@ -8,6 +8,10 @@ b = [4, 5, 6]
 del b[1]
 del b[:]
 
+# del_stmt ::= expr expr DELETE_SLICE+1
+l = [None] * 10
+del l[-2:]
+
 c = [0,1,2,3,4]
 del c[:1]
 del c[2:3]
@@ -22,8 +26,10 @@ def foo():
     del e
 
 def a():
+    b =1
     del z
     def b(y):
+        global z
         # covers DELETE_FAST
         del y
         # LOAD_DEREF