Source file f.flush() after writing; trying to avoid lossage if user
kills GUI.  Report from B. Sherwood.  Backport to 2.3.4.
diff --git a/Lib/idlelib/IOBinding.py b/Lib/idlelib/IOBinding.py
index ce1fd2a..deeb5c5 100644
--- a/Lib/idlelib/IOBinding.py
+++ b/Lib/idlelib/IOBinding.py
@@ -377,6 +377,7 @@
         try:
             f = open(filename, "wb")
             f.write(chars)
+            f.flush()
             f.close()
             return True
         except IOError, msg: