preparing release of libxml2-2.6.27 fix a small problem with preproc flags

* NEWS configure.in testapi.c doc//*: preparing release of
  libxml2-2.6.27
* include/libxml/tree.h: fix a small problem with preproc flags
Daniel
diff --git a/doc/devhelp/libxml2-tree.html b/doc/devhelp/libxml2-tree.html
index aba84d3..70c6e50 100644
--- a/doc/devhelp/libxml2-tree.html
+++ b/doc/devhelp/libxml2-tree.html
@@ -1081,7 +1081,7 @@
         <hr/>
         <div class="refsect2" lang="en"><h3><a name="xmlDocSetRootElement"/>xmlDocSetRootElement ()</h3><pre class="programlisting"><a href="libxml2-tree.html#xmlNodePtr">xmlNodePtr</a>	xmlDocSetRootElement	(<a href="libxml2-tree.html#xmlDocPtr">xmlDocPtr</a> doc, <br/>					 <a href="libxml2-tree.html#xmlNodePtr">xmlNodePtr</a> root)<br/>
 </pre><p>Set the root element of the document (doc-&gt;children is a list containing possibly comments, PIs, etc ...).</p>
-<div class="variablelist"><table border="0"><col align="left"/><tbody><tr><td><span class="term"><i><tt>doc</tt></i>:</span></td><td>the document</td></tr><tr><td><span class="term"><i><tt>root</tt></i>:</span></td><td>the new document root element</td></tr><tr><td><span class="term"><i><tt>Returns</tt></i>:</span></td><td>the old root element if any was found</td></tr></tbody></table></div></div>
+<div class="variablelist"><table border="0"><col align="left"/><tbody><tr><td><span class="term"><i><tt>doc</tt></i>:</span></td><td>the document</td></tr><tr><td><span class="term"><i><tt>root</tt></i>:</span></td><td>the new document root element, if root is NULL no action is taken, to remove a node from a document use xmlUnlinkNode(root) instead.</td></tr><tr><td><span class="term"><i><tt>Returns</tt></i>:</span></td><td>the old root element if any was found, NULL if root was NULL</td></tr></tbody></table></div></div>
         <hr/>
         <div class="refsect2" lang="en"><h3><a name="xmlElemDump"/>xmlElemDump ()</h3><pre class="programlisting">void	xmlElemDump			(FILE * f, <br/>					 <a href="libxml2-tree.html#xmlDocPtr">xmlDocPtr</a> doc, <br/>					 <a href="libxml2-tree.html#xmlNodePtr">xmlNodePtr</a> cur)<br/>
 </pre><p>Dump an XML/HTML node, recursive behaviour, children are printed too.</p>