applied patch from Alfred Mickautsch, bugfixes and comments added his test

* xmlwriter.c include/libxml/xmlwriter.h: applied patch from
  Alfred Mickautsch, bugfixes and comments
* doc/examples/*: added his test as the xmlWriter example
* doc/html/ doc/*.html: this resulted in some improvements
* include/libxml/hash.h: fixed an inclusion problem when
  <libxml/hash.h> wasn't preceeded by <xml/parser.h>
Daniel
diff --git a/doc/APIsymbols.html b/doc/APIsymbols.html
index 4ccd064..9f83808 100644
--- a/doc/APIsymbols.html
+++ b/doc/APIsymbols.html
@@ -1767,8 +1767,11 @@
 <a href="html/libxml-xmlreader.html#xmlNewTextReader">xmlNewTextReader</a><br />
 <a href="html/libxml-xmlreader.html#xmlNewTextReaderFilename">xmlNewTextReaderFilename</a><br />
 <a href="html/libxml-xmlwriter.html#xmlNewTextWriter">xmlNewTextWriter</a><br />
+<a href="html/libxml-xmlwriter.html#xmlNewTextWriterDoc">xmlNewTextWriterDoc</a><br />
 <a href="html/libxml-xmlwriter.html#xmlNewTextWriterFilename">xmlNewTextWriterFilename</a><br />
 <a href="html/libxml-xmlwriter.html#xmlNewTextWriterMemory">xmlNewTextWriterMemory</a><br />
+<a href="html/libxml-xmlwriter.html#xmlNewTextWriterPushParser">xmlNewTextWriterPushParser</a><br />
+<a href="html/libxml-xmlwriter.html#xmlNewTextWriterTree">xmlNewTextWriterTree</a><br />
 <a href="html/libxml-valid.html#xmlNewValidCtxt">xmlNewValidCtxt</a><br />
 <a href="html/libxml-parserInternals.html#xmlNextChar">xmlNextChar</a><br />
 <a href="html/libxml-xmlIO.html#xmlNoNetExternalEntityLoader">xmlNoNetExternalEntityLoader</a><br />