schema compile CHANGE remember the module where default value was defined

To be able to recompile the default value (in typedef, leaf or
leaf-list), it is necessary to know in which module the value was
defined to be able to correctly resolve prefixes possibly used in the
value.
diff --git a/src/tree_schema_free.c b/src/tree_schema_free.c
index b78e158..8383c19 100644
--- a/src/tree_schema_free.c
+++ b/src/tree_schema_free.c
@@ -717,6 +717,7 @@
         free(node->dflts[u]);
     }
     LY_ARRAY_FREE(node->dflts);
+    LY_ARRAY_FREE(node->dflts_mods);
 }
 
 static void