Spelling fixes supplied by Rob W. W. Hooft. All these are fixes in either
comments, docstrings or error messages. I fixed two minor things in
test_winreg.py ("didn't" -> "Didn't" and "Didnt" -> "Didn't").

There is a minor style issue involved: Guido seems to have preferred English
grammar (behaviour, honour) in a couple places. This patch changes that to
American, which is the more prominent style in the source. I prefer English
myself, so if English is preferred, I'd be happy to supply a patch myself ;)
diff --git a/Lib/test/test_pty.py b/Lib/test/test_pty.py
index d6dd1d7..389d2a7 100644
--- a/Lib/test/test_pty.py
+++ b/Lib/test/test_pty.py
@@ -66,7 +66,7 @@
         pass
     except:
         # We don't want this error to propagate, escape the call to
-        # os._exit(), and cause very peculiar behaviour in the calling
+        # os._exit(), and cause very peculiar behavior in the calling
         # regrtest.py !
         debug("Some other error was raised.")
         os._exit(1)