Fix bug with IOLoop's 'waker' pipe which rendered it ineffective on l…

…inux

and mac (where pipes are unidirectional) and caused high cpu usage
on solaris (where pipes are bidirectional).  Thanks to Jari Ahonen for
finding the bug.

tornado/ioloop.py

@@ -99,7 +99,7 @@ def __init__(self, impl=None):
         self._set_close_exec(w)
         self._waker_reader = os.fdopen(r, "r", 0)
         self._waker_writer = os.fdopen(w, "w", 0)
-        self.add_handler(r, self._read_waker, self.WRITE)
+        self.add_handler(r, self._read_waker, self.READ)
 
     @classmethod
     def instance(cls):