libyang FEATURE add lyd_get_value() and lyd_get_meta_value()

Avoid direct accessing of value's canonical member using the new
functions or (internaly) by using the type's print callback.
diff --git a/tests/utests/basic/test_xpath.c b/tests/utests/basic/test_xpath.c
index 24e9baa..a26a51f 100644
--- a/tests/utests/basic/test_xpath.c
+++ b/tests/utests/basic/test_xpath.c
@@ -151,7 +151,7 @@
     assert_string_equal(node->schema->name, "l1");
     node = lyd_child(node);
     assert_string_equal(node->schema->name, "a");
-    assert_string_equal(LYD_CANON_VALUE(node), "a3");
+    assert_string_equal(lyd_get_value(node), "a3");
 
     ly_set_free(set, NULL);
 
@@ -163,7 +163,7 @@
     assert_string_equal(node->schema->name, "ll");
     node = lyd_child(node);
     assert_string_equal(node->schema->name, "a");
-    assert_string_equal(LYD_CANON_VALUE(node), "val_b");
+    assert_string_equal(lyd_get_value(node), "val_b");
     node = node->next;
     assert_string_equal(node->schema->name, "b");
     assert_null(node->next);
@@ -182,7 +182,7 @@
 
     node = set->objs[0];
     assert_string_equal(node->schema->name, "ll2");
-    assert_string_equal(LYD_CANON_VALUE(node), "three");
+    assert_string_equal(lyd_get_value(node), "three");
 
     ly_set_free(set, NULL);