adds element traversal support avoid a warning regenerated daniel

* include/libxml/tree.h tree.c python/generator.py: adds
  element traversal support
* valid.c: avoid a warning
* doc/*: regenerated
daniel

svn path=/trunk/; revision=3804
diff --git a/python/generator.py b/python/generator.py
index 4e22815..92a3440 100755
--- a/python/generator.py
+++ b/python/generator.py
@@ -725,6 +725,10 @@
     "xmlDocSetRootElement": 1,
     "xmlNodeGetNs": 1,
     "xmlNodeGetNsDefs": 1,
+    "xmlNextElementSibling": 1,
+    "xmlPreviousElementSibling": 1,
+    "xmlFirstElementChild": 1,
+    "xmlLastElementChild": 1,
 }
 
 reference_keepers = {
diff --git a/python/libxml2class.txt b/python/libxml2class.txt
index 68a2de1..1b8db59 100644
--- a/python/libxml2class.txt
+++ b/python/libxml2class.txt
@@ -457,6 +457,7 @@
     docCopyNode()
     docCopyNodeList()
     docSetRootElement()
+    firstElementChild()
     freeNode()
     freeNodeList()
     getBase()
@@ -468,6 +469,7 @@
     isBlankNode()
     isText()
     lastChild()
+    lastElementChild()
     lineNo()
     listGetRawString()
     listGetString()
@@ -477,9 +479,11 @@
     newNsPropEatName()
     newProp()
     newTextChild()
+    nextElementSibling()
     noNsProp()
     nodePath()
     nsProp()
+    previousElementSibling()
     prop()
     reconciliateNs()
     replaceNode()