integrated Eric Lavigne (sp???) contribution to build libxml2 on MacOS

* configure.in libxml.h parser.c testThreads.c macos/: integrated
  Eric Lavigne (sp???) contribution to build libxml2 on MacOS using
  CodeWarrior.
Daniel
diff --git a/libxml.h b/libxml.h
index aaebf3b..6b7476f 100644
--- a/libxml.h
+++ b/libxml.h
@@ -11,6 +11,8 @@
 
 #if defined(WIN32) && !defined(__CYGWIN__)
 #include "win32config.h"
+#elif defined(macintosh)
+#include "config-mac.h"
 #else
 #include "config.h"
 #include <libxml/xmlversion.h>