Shift+arrow sends only arrow key

Shift + arrow sending only arrow key. E.g.:
```
kb.SetKeys(keybd_event.VK_LEFT) 
kb.HasSHIFT(true) 
kb.Press()
time.Sleep(10 * time.Millisecond)
kb.Release()
```
sends left key press without shift (easy check: in any textfield it should select text, not just move caret).