QueryValue should also retrieve the key's unnamed value, if any.

```
It is documented by Microsoft that RegQueryValueEx returns the unnamed/
default value of the key (if available) when the lpValueName argument is 
null or an empty string. The virtual registry should also implement this 
behavior.

http://msdn.microsoft.com/en-us/library/ms724911(VS.85).aspx
```

Original issue reported on code.google.com by `simon_al...@hotmail.com` on 12 May 2009 at 7:26
