crypto: use X509V3_EXT_d2i

There is no need to reach into quite so many internals to decode an
extension.

src/node_crypto.cc

@@ -1483,12 +1483,7 @@ static bool SafeX509ExtPrint(BIO* out, X509_EXTENSION* ext) {
   if (method != X509V3_EXT_get_nid(NID_subject_alt_name))
     return false;
 
-  const unsigned char* p = ext->value->data;
-  GENERAL_NAMES* names = reinterpret_cast<GENERAL_NAMES*>(ASN1_item_d2i(
-      NULL,
-      &p,
-      ext->value->length,
-      ASN1_ITEM_ptr(method->it)));
+  GENERAL_NAMES* names = static_cast<GENERAL_NAMES*>(X509V3_EXT_d2i(ext));
   if (names == NULL)
     return false;