configure: Add a check for xmlDocProperties.
diff --git a/configure.ac b/configure.ac
index f38aca4..f0ebc03 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1121,6 +1121,8 @@
                 [AC_DEFINE(HAVE_XMLNEWDOCPI,1,[Define if libxml2 has the xmlNewDocPI function])],,$ac_xml_libs)
              AC_CHECK_LIB(xml2, xmlSchemaSetValidStructuredErrors,
                 [AC_DEFINE(HAVE_XMLSCHEMASSETVALIDSTRUCTUREDERRORS,1,[Define if libxml2 has the xmlSchemaSetValidStructuredErrors function])],,$ac_xml_libs)
+             AC_CHECK_TYPE([xmlDocProperties],
+                [AC_DEFINE(HAVE_XMLDOC_PROPERTIES,1,[Define if libxml2 has the xmlDocProperties enum])],,[[#include <libxml/tree.h>]])
         ])
     CPPFLAGS="$ac_save_CPPFLAGS"
 fi