Update link to the zlib homepage.

Doc/lib/libzlib.tex

@@ -9,10 +9,10 @@
 For applications that require data compression, the functions in this
 module allow compression and decompression, using the zlib library.
 The zlib library has its own home page at
-\url{http://www.cdrom.com/pub/infozip/zlib/}.  Version 1.1.3 is the
-most recent version as of April 1999; use a later version if one
-is available.  There are known incompatibilities between the Python
-module and earlier versions of the zlib library.
+\url{ftp://ftp.freesoftware.com/pub/infozip/zlib/zlib.html}.  Version
+1.1.3 is the most recent version as of September 2000; use a later
+version if one is available.  There are known incompatibilities
+between the Python module and earlier versions of the zlib library.
 
 The available exception and functions in this module are: