make sure the parser flags and passed onto the compiler

This fixes "from __future__ import unicode_literals" in an exec statment
See #4225
diff --git a/Misc/NEWS b/Misc/NEWS
index 3017d4b..234a15d 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -12,6 +12,9 @@
 Core and Builtins
 -----------------
 
+- Issue #4225: ``from __future__ import unicode_literals`` didn't work in an
+  exec statement.
+
 - Issue #4176: Fixed a crash when pickling an object which ``__reduce__``
   method does not return iterators for the 4th and 5th items.