Add test case for global stmt at module level.
Fix test_grammar so that it ignores warning about global stmt at
module level in exec.
diff --git a/Lib/test/test_global.py b/Lib/test/test_global.py
index c60d0c7..b41b7d4 100644
--- a/Lib/test/test_global.py
+++ b/Lib/test/test_global.py
@@ -37,3 +37,9 @@
     global x
 """
 compile_and_catch_warning(prog_text_3)
+
+prog_text_4 = """
+global x
+x = 2
+"""
+compile_and_catch_warning(prog_text_4)