buffer: alias toLocaleString to toString

Make Buffer.prototype.toLocaleString an alias of Buffer.prototype.toString
so that the output is actually useful.

Fixes: https://github.com/nodejs/node/issues/8147
PR-URL: https://github.com/nodejs/node/pull/8148
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Trevor Norris <trev.norris@gmail.com>

lib/buffer.js

@@ -1332,3 +1332,5 @@ Buffer.prototype.swap64 = function swap64() {
   }
   return swap64n(this);
 };
+
+Buffer.prototype.toLocaleString = Buffer.prototype.toString;

test/parallel/test-buffer-alloc.js

@@ -1502,3 +1502,9 @@ assert.throws(() => Buffer.alloc({ valueOf: () => 1 }),
               /"size" argument must be a number/);
 assert.throws(() => Buffer.alloc({ valueOf: () => -1 }),
               /"size" argument must be a number/);
+
+assert.strictEqual(Buffer.prototype.toLocaleString, Buffer.prototype.toString);
+{
+  const buf = Buffer.from('test');
+  assert.strictEqual(buf.toLocaleString(), buf.toString());
+}