structure FEATURE support for ietf-yang-structure-ext

Only for the structure itself, no augment yet.
diff --git a/src/plugins.c b/src/plugins.c
index 70b23b8..28fcd0e 100644
--- a/src/plugins.c
+++ b/src/plugins.c
@@ -84,6 +84,7 @@
 extern struct lyplg_ext_record plugins_nacm[];
 extern struct lyplg_ext_record plugins_yangdata[];
 extern struct lyplg_ext_record plugins_schema_mount[];
+extern struct lyplg_ext_record plugins_structure[];
 
 static pthread_mutex_t plugins_guard = PTHREAD_MUTEX_INITIALIZER;
 
@@ -469,6 +470,7 @@
     LY_CHECK_GOTO(ret = plugins_insert(LYPLG_EXTENSION, plugins_nacm), error);
     LY_CHECK_GOTO(ret = plugins_insert(LYPLG_EXTENSION, plugins_yangdata), error);
     LY_CHECK_GOTO(ret = plugins_insert(LYPLG_EXTENSION, plugins_schema_mount), error);
+    LY_CHECK_GOTO(ret = plugins_insert(LYPLG_EXTENSION, plugins_structure), error);
 
 #ifndef STATIC
     /* external types */