Update url.

Old url returned status code:301 Moved permanently.
diff --git a/Doc/lib/libzipfile.tex b/Doc/lib/libzipfile.tex
index d7c08f6..47d1e5a 100644
--- a/Doc/lib/libzipfile.tex
+++ b/Doc/lib/libzipfile.tex
@@ -13,8 +13,8 @@
 This module provides tools to create, read, write, append, and list a
 ZIP file.  Any advanced use of this module will require an
 understanding of the format, as defined in
-\citetitle[http://www.pkware.com/appnote.html]{PKZIP Application
-Note}.
+\citetitle[http://www.pkware.com/business_and_developers/developer/appnote/]
+{PKZIP Application Note}.
 
 This module does not currently handle ZIP files which have appended
 comments, or multi-disk ZIP files. It can handle ZIP files that use the 
@@ -71,9 +71,9 @@
 
 
 \begin{seealso}
-  \seetitle[http://www.pkware.com/appnote.html]{PKZIP Application
-            Note}{Documentation on the ZIP file format by Phil
-            Katz, the creator of the format and algorithms used.}
+  \seetitle[http://www.pkware.com/business_and_developers/developer/appnote/]
+           {PKZIP Application Note}{Documentation on the ZIP file format by
+            Phil Katz, the creator of the format and algorithms used.}
 
   \seetitle[http://www.info-zip.org/pub/infozip/]{Info-ZIP Home Page}{
             Information about the Info-ZIP project's ZIP archive
@@ -255,9 +255,9 @@
 
 \begin{memberdesc}[ZipInfo]{extra}
   Expansion field data.  The
-  \citetitle[http://www.pkware.com/appnote.html]{PKZIP Application
-  Note} contains some comments on the internal structure of the data
-  contained in this string.
+  \citetitle[http://www.pkware.com/business_and_developers/developer/appnote/]
+  {PKZIP Application Note} contains some comments on the internal
+  structure of the data contained in this string.
 \end{memberdesc}
 
 \begin{memberdesc}[ZipInfo]{create_system}