yanglint FEATURE --extended-leafref for add, load

... commands in interactive mode.
diff --git a/tools/lint/cmd_load.c b/tools/lint/cmd_load.c
index 488293e..797167c 100644
--- a/tools/lint/cmd_load.c
+++ b/tools/lint/cmd_load.c
@@ -39,7 +39,9 @@
             "  -i, --make-implemented\n"
             "                  Make the imported modules \"referenced\" from any loaded\n"
             "                  <schema> module also implemented. If specified a second time,\n"
-            "                  all the modules are set implemented.\n");
+            "                  all the modules are set implemented.\n"
+            "  -X, --extended-leafref\n"
+            "                  Allow usage of deref() XPath function within leafref.\n");
 }
 
 void
@@ -52,6 +54,7 @@
         {"features", required_argument, NULL, 'F'},
         {"help", no_argument, NULL, 'h'},
         {"make-implemented", no_argument, NULL, 'i'},
+        {"extended-leafref", no_argument, NULL, 'X'},
         {NULL, 0, NULL, 0}
     };
     uint16_t options_ctx = 0;
@@ -83,6 +86,10 @@
             }
             break;
 
+        case 'X': /* --extended-leafref */
+            options_ctx |= LY_CTX_LEAFREF_EXTENDED;
+            break;
+
         default:
             YLMSG_E("Unknown option.\n");
             goto cleanup;