hack based on Arjan van de Ven suggestion to reduce ELF footprint and

* elfgcchack.h doc/elfgcchack.xsl libxml.h: hack based on Arjan van de
  Ven suggestion to reduce ELF footprint and generated code. Based on
  aliasing of libraries function to generate direct call instead of
  indirect ones
* doc/libxml2-api.xml doc/Makefile.am doc/apibuild.py: added automatic
  generation of elfgcchack.h based on the API description, extended
  the API description to show the conditionals configuration flags
  required for symbols.
* nanohttp.c parser.c xmlsave.c include/libxml/*.h: lot of cleanup
* doc/*: regenerated the docs.
Daniel

parser.c

@@ -1039,6 +1039,8 @@ nodePop(xmlParserCtxtPtr ctxt)
     ctxt->nodeTab[ctxt->nodeNr] = 0;
     return (ret);
 }
+
+#ifdef LIBXML_PUSH_ENABLED
 /**
  * nameNsPush:
  * @ctxt:  an XML parser context
@@ -1109,6 +1111,7 @@ nameNsPop(xmlParserCtxtPtr ctxt)
     ctxt->nameTab[ctxt->nameNr] = NULL;
     return (ret);
 }
+#endif /* LIBXML_PUSH_ENABLED */
 
 /**
  * namePush: