Re-examined the problems of configuring a "minimal" library.

Synchronized the header files with the library code in order
to assure that all the various conditionals (LIBXML_xxxx_ENABLED)
were the same in both.  Modified the API database content to more
accurately reflect the conditionals.  Enhanced the generation
of that database.  Although there was no substantial change to
any of the library code's logic, a large number of files were
modified to achieve the above, and the configuration script
was enhanced to do some automatic enabling of features (e.g.
--with-xinclude forces --with-xpath).  Additionally, all the format
errors discovered by apibuild.py were corrected.
* configure.in: enhanced cross-checking of options
* doc/apibuild.py, doc/elfgcchack.xsl, doc/libxml2-refs.xml,
  doc/libxml2-api.xml, gentest.py: changed the usage of the
  <cond> element in module descriptions
* elfgcchack.h, testapi.c: regenerated with proper conditionals
* HTMLparser.c, SAX.c, globals.c, tree.c, xmlschemas.c, xpath.c,
  testSAX.c: cleaned up conditionals
* include/libxml/[SAX.h, SAX2.h, debugXML.h, encoding.h, entities.h,
  hash.h, parser.h, parserInternals.h, schemasInternals.h, tree.h,
  valid.h, xlink.h, xmlIO.h, xmlautomata.h, xmlreader.h, xpath.h]:
  synchronized the conditionals with the corresponding module code
* doc/examples/tree2.c, doc/examples/xpath1.c, doc/examples/xpath2.c:
  added additional conditions required for compilation
* doc/*.html, doc/html/*.html: rebuilt the docs

include/libxml/SAX.h

@@ -18,7 +18,7 @@
 #include <libxml/parser.h>
 #include <libxml/xlink.h>
 
-#ifdef LIBXML_SAX1_ENABLED
+#ifdef LIBXML_LEGACY_ENABLED
 
 #ifdef __cplusplus
 extern "C" {
@@ -150,6 +150,7 @@ XMLPUBFUN void XMLCALL
 						 const xmlChar *value,
 						 int len);
 
+#ifdef LIBXML_SAX1_ENABLED
 XMLPUBFUN void XMLCALL		
 		initxmlDefaultSAXHandler	(xmlSAXHandlerV1 *hdlr,
 						 int warning);
@@ -161,10 +162,12 @@ XMLPUBFUN void XMLCALL
 XMLPUBFUN void XMLCALL		
 		initdocbDefaultSAXHandler	(xmlSAXHandlerV1 *hdlr);
 #endif
+#endif /* LIBXML_SAX1_ENABLED */
+
 #ifdef __cplusplus
 }
 #endif
 
-#endif /* LIBXML_SAX1_ENABLED */
+#endif /* LIBXML_LEGACY_ENABLED */
 
 #endif /* __XML_SAX_H__ */