Avoid a few 301 permanent redirects.

Part of SF patch #773007.

Doc/whatsnew/whatsnew21.tex

@@ -576,7 +576,7 @@ operations will now be processed at the C level.}
 
 A common complaint from Python users is that there's no single catalog
 of all the Python modules in existence.  T.~Middleton's Vaults of
-Parnassus at \url{http://www.vex.net/parnassus} are the largest
+Parnassus at \url{http://www.vex.net/parnassus/} are the largest
 catalog of Python modules, but registering software at the Vaults is
 optional, and many people don't bother.
 
@@ -599,7 +599,7 @@ you're not using Python 2.1, since a new release of the Distutils will
 be made for users of earlier Python versions.  Version 1.0.2 of the
 Distutils includes the changes described in PEP 241, as well as
 various bugfixes and enhancements.  It will be available from 
-the Distutils SIG at \url{http://www.python.org/sigs/distutils-sig}.
+the Distutils SIG at \url{http://www.python.org/sigs/distutils-sig/}.
 
 % XXX update when I actually release 1.0.2
 
@@ -797,7 +797,7 @@ for line in sys.stdin.xreadlines():
 
 For a fuller discussion of the line I/O changes, see the python-dev
 summary for January 1-15, 2001 at
-\url{http://www.amk.ca/python/dev/2001-01-1.html}.
+\url{http://www.python.org/dev/summary/2001-01-1.html}.
 
 \item A new method, \method{popitem()}, was added to dictionaries to
 enable destructively iterating through the contents of a dictionary;