fixed bug with static unicode strings and auto escaping

--HG--
branch : trunk
diff --git a/jinja2/environment.py b/jinja2/environment.py
index 95dda11..45d684d 100644
--- a/jinja2/environment.py
+++ b/jinja2/environment.py
@@ -642,8 +642,7 @@
 
     def __init__(self, gen):
         self._gen = gen
-        self._next = gen.next
-        self.buffered = False
+        self.disable_buffering()
 
     def disable_buffering(self):
         """Disable the output buffering."""