fixing compilation and link option when configuring with --without-valid

* debugXML.c relaxng.c valid.c xinclude.c xmllint.c xmlreader.c:
  fixing compilation and link option when configuring with
  --without-valid should fix #135309
Daniel
diff --git a/debugXML.c b/debugXML.c
index bcb1fcd..25c1d15 100644
--- a/debugXML.c
+++ b/debugXML.c
@@ -1955,6 +1955,7 @@
 }
 #endif /* LIBXML_OUTPUT_ENABLED */
 
+#ifdef LIBXML_VALID_ENABLED
 /**
  * xmlShellValidate:
  * @ctxt:  the shell context
@@ -1994,6 +1995,7 @@
     }
     return (res);
 }
+#endif /* LIBXML_VALID_ENABLED */
 
 /**
  * xmlShellDu:
@@ -2249,13 +2251,17 @@
 		  fprintf(ctxt->output, "\tsave [name]  save this document to name or the original name\n");
 		  fprintf(ctxt->output, "\twrite [name] write the current node to the filename\n");
 #endif /* LIBXML_OUTPUT_ENABLED */
+#ifdef LIBXML_VALID_ENABLED
 		  fprintf(ctxt->output, "\tvalidate     check the document for errors\n");
+#endif /* LIBXML_VALID_ENABLED */
 #ifdef LIBXML_SCHEMAS_ENABLED
 		  fprintf(ctxt->output, "\trelaxng rng  validate the document agaisnt the Relax-NG schemas\n");
 #endif
 		  fprintf(ctxt->output, "\tgrep string  search for a string in the subtree\n");
+#ifdef LIBXML_VALID_ENABLED
         } else if (!strcmp(command, "validate")) {
             xmlShellValidate(ctxt, arg, NULL, NULL);
+#endif /* LIBXML_VALID_ENABLED */
         } else if (!strcmp(command, "load")) {
             xmlShellLoad(ctxt, arg, NULL, NULL);
 #ifdef LIBXML_SCHEMAS_ENABLED