Use default instead of empty

Author: lucic71

rules/stdarg/ir_unsafe.json

@@ -1,6 +1,6 @@
 {
   "t1": {
-    "init": "VaList::empty()",
+    "init": "VaList::default()",
     "type": "VaList"
   }
 }

rules/stdarg/tgt_unsafe.rs

@@ -1,5 +1,5 @@
 use libcc2rs::VaList;
 
 fn types() {
-    let t1: VaList = VaList::empty();
+    let t1: VaList = VaList::default();
 }