Double double quotes

After recently updating xmldom to newest version I have started getting bad XML on the output in the form of

```
<!DOCTYPE svg PUBLIC ""-//W3C//DTD SVG 1.1//EN"" ""http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd"">
```
Note the double double-quotes. I am not sure if my commit does not break anything else ... anyhow - please take take a look! Thanks for a useful module.