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/configure.in b/configure.in
index 77a4943..192dfae 100644
--- a/configure.in
+++ b/configure.in
@@ -388,6 +388,8 @@
 # include <arpa/nameser.h>
 # endif
 ])
+AC_CHECK_HEADERS([dl.h])
+AC_CHECK_HEADERS([dlfcn.h])
 
 
 echo Checking libraries