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/src/printer_lyb.c b/src/printer_lyb.c
index 83ac1e8..c1e80df 100644
--- a/src/printer_lyb.c
+++ b/src/printer_lyb.c
@@ -699,7 +699,7 @@
 lyb_print_term(struct lyd_node_term *term, struct ly_out *out, struct lylyb_ctx *lybctx)
 {
     /* print the value */
-    return lyb_write_string(LYD_CANON_VALUE(term), 0, 0, out, lybctx);
+    return lyb_write_string(lyd_get_value(&term->node), 0, 0, out, lybctx);
 }
 
 /**
@@ -762,7 +762,7 @@
         LY_CHECK_RET(lyb_write_string(iter->name, 0, 1, out, lybctx->lybctx));
 
         /* metadata value */
-        LY_CHECK_RET(lyb_write_string(iter->value.canonical, 0, 0, out, lybctx->lybctx));
+        LY_CHECK_RET(lyb_write_string(lyd_get_meta_value(iter), 0, 0, out, lybctx->lybctx));
 
         /* finish metadata subtree */
         LY_CHECK_RET(lyb_write_stop_subtree(out, lybctx->lybctx));