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/xmllib.py b/Lib/xmllib.py
index bbd4b54..06b599f 100644
--- a/Lib/xmllib.py
+++ b/Lib/xmllib.py
@@ -143,7 +143,7 @@
         self.__seen_starttag = 0
         self.__use_namespaces = 0
         self.__namespaces = {'xml':None}   # xml is implicitly declared
-        # backward compatipibility hack: if elements not overridden,
+        # backward compatibility hack: if elements not overridden,
         # fill it in ourselves
         if self.elements is XMLParser.elements:
             self.__fixelements()