trying to work around the compilation problem on HP-UX Daniel

* config.h.in configure.in xmlmodule.c: trying to work around
  the compilation problem on HP-UX
Daniel
diff --git a/config.h.in b/config.h.in
index a7b6eeb..141486d 100644
--- a/config.h.in
+++ b/config.h.in
@@ -43,6 +43,9 @@
 /* Have dlopen based dso */
 #undef HAVE_DLOPEN
 
+/* Define to 1 if you have the <dl.h> header file. */
+#undef HAVE_DL_H
+
 /* Define to 1 if you have the <errno.h> header file. */
 #undef HAVE_ERRNO_H