yanglint FEATURE do not load ietf-yang-library by default

To avoid validation errors caused by this module.
Fixes #1371
diff --git a/tools/lint/common.c b/tools/lint/common.c
index 796a450..968d00f 100644
--- a/tools/lint/common.c
+++ b/tools/lint/common.c
@@ -345,7 +345,7 @@
 
     if (outformat != LYD_UNKNOWN) {
         if (ly_ctx_get_yanglib_data(ctx, &ylib)) {
-            YLMSG_E("Getting context info (ietf-yang-library data) failed.\n");
+            YLMSG_E("Getting context info (ietf-yang-library data) failed. If the YANG module is missing or not implemented, use an option to add it internally.\n");
             return 1;
         }