fs.accessSync() with W_OK throws EPERM for directories in Windows

iojs 1.6.4 x86 under Windows 8.1 64 bit

```
> fs.accessSync(os.tmpDir(), fs.W_OK)
Error: EPERM: operation not permitted, access 'C:\Users\alex\AppData\Local\Temp'
```

The same check for a directory works fine in Linux:

```
> fs.accessSync(os.tmpDir(), fs.W_OK)
undefined
```
