The selector engine doesn't support the HEX escaped characters

We have:
HTML fragment: 

```
<div id="B&W?"><p>test</p></div>
```

Selector:

```
#B\\26 W\\3F
```

And it doesn't work. Returns 0 elements. Following this document http://www.w3.org/TR/CSS2/syndata.html#characters CSS identifier (or selector) may contain any ISO 10646 character as a numeric code (or HEX code, as I show here).
