Could tabs be preserved inside <pre> blocks?

Running tidy on this doc (→ represents a tab character):

``` html
<!DOCTYPE html>
<title>pre test</title>
<pre>→A,
→B,
→C,</pre>
```

changes how the document looks in browsers, as tidy replaces the tabs with spaces.

Before tidy:

```
    A,
    B,
    C,
```

After tidy:

```
   A,
        B,
        C,
```
