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/PC/_winreg.c b/PC/_winreg.c
index 75ceb8b..84bf3c4 100644
--- a/PC/_winreg.c
+++ b/PC/_winreg.c
@@ -658,7 +658,7 @@
 ** Note that fixupMultiSZ and countString have both had changes
 ** made to support "incorrect strings".  The registry specification
 ** calls for strings to be terminated with 2 null bytes.  It seems
-** some commercial packages install strings whcich dont conform,
+** some commercial packages install strings which dont conform,
 ** causing this code to fail - however, "regedit" etc still work
 ** with these strings (ie only we dont!).
 */