[svn-r4219] Purpose:

Linking to new "Freespace Management" section from appropriate places.
Description:
    Added links, with explanatory paragraph or footnote,
    from Chunking.html, Filters.html, and H5Gunlink in RM_H5G.html
    to "Freespace Management" in Performance.html.
Platforms tested:
    IE 5

doc/html/Performance.html

@@ -63,7 +63,9 @@
       <a href="Chunking.html">Dataset Chunking Issues</a> elsewhere
       in this <cite>User's Guide</cite>.
 
+    <a name="Freespace">
     <h2>3. Freespace Management</h2>
+    </a>
 
      <p>HDF5 does not yet manage freespace as effectively as it might.
       While a file is opened, the library actively tracks and re-uses