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
diff --git a/include/libxml/DOCBparser.h b/include/libxml/DOCBparser.h
index d30aaea..461d4ee 100644
--- a/include/libxml/DOCBparser.h
+++ b/include/libxml/DOCBparser.h
@@ -11,6 +11,9 @@
 #ifndef __DOCB_PARSER_H__
 #define __DOCB_PARSER_H__
 #include <libxml/xmlversion.h>
+
+#ifdef LIBXML_DOCB_ENABLED
+
 #include <libxml/parser.h>
 #include <libxml/parserInternals.h>
 
@@ -87,4 +90,7 @@
 #ifdef __cplusplus
 }
 #endif
+
+#endif /* LIBXML_DOCB_ENABLED */
+
 #endif /* __DOCB_PARSER_H__ */