fixed xmlXPathReturnString to cater for NULL pointer (bug 129561) added

* include/libxml/xpathInternals.h: fixed xmlXPathReturnString
  to cater for NULL pointer (bug 129561)
* globals.c: added comment to suppress documentation warning
* doc/apibuild.py: fixed problem which caused last APIchunkxx.html
  to be lost.  Rebuilt doc/* (including adding APIchunk26.html)
diff --git a/doc/APIchunk0.html b/doc/APIchunk0.html
index 8bbf43f..e0f946a 100644
--- a/doc/APIchunk0.html
+++ b/doc/APIchunk0.html
@@ -33,6 +33,7 @@
 <a href="APIchunk23.html">t-t</a>
 <a href="APIchunk24.html">u-w</a>
 <a href="APIchunk25.html">x-x</a>
+<a href="APIchunk26.html">y-z</a>
 </h2><h2>Letter A:</h2><dl><dt>A-Z</dt><dd><a href="html/libxml-parserInternals.html#xmlCheckLanguageID">xmlCheckLanguageID</a><br />
 </dd><dt>A-Za-z</dt><dd><a href="html/libxml-parserInternals.html#xmlParseEncName">xmlParseEncName</a><br />
 </dd><dt>A-Za-z0-9</dt><dd><a href="html/libxml-parserInternals.html#xmlParseEncName">xmlParseEncName</a><br />
@@ -102,6 +103,8 @@
 <a href="html/libxml-hash.html#xmlHashUpdateEntry2">xmlHashUpdateEntry2</a><br />
 <a href="html/libxml-hash.html#xmlHashUpdateEntry3">xmlHashUpdateEntry3</a><br />
 </dd><dt>Additional</dt><dd><a href="html/libxml-HTMLparser.html#_htmlElemDesc">_htmlElemDesc</a><br />
+<a href="html/libxml-globals.html#xmlCleanupGlobals">xmlCleanupGlobals</a><br />
+<a href="html/libxml-globals.html#xmlInitGlobals">xmlInitGlobals</a><br />
 </dd><dt>AegeanNumbers</dt><dd><a href="html/libxml-xmlunicode.html#xmlUCSIsAegeanNumbers">xmlUCSIsAegeanNumbers</a><br />
 </dd><dt>All</dt><dd><a href="html/libxml-nanoftp.html#xmlNanoFTPGet">xmlNanoFTPGet</a><br />
 <a href="html/libxml-nanoftp.html#xmlNanoFTPList">xmlNanoFTPList</a><br />
@@ -270,4 +273,5 @@
 <a href="APIchunk23.html">t-t</a>
 <a href="APIchunk24.html">u-w</a>
 <a href="APIchunk25.html">x-x</a>
+<a href="APIchunk26.html">y-z</a>
 </h2><p><a href="bugs.html">Daniel Veillard</a></p></td></tr></table></td></tr></table></td></tr></table></td></tr></table></td></tr></table></body></html>