declaration formatting improvement

[Wade Brainerd]

Hi, this patch improves the formatting of the declaration node. Normally, if you were to set version to 1.0 and encoding to utf-8, you get:

<?xml version="1.0" encoding="utf-8" ?>

With this patch, you get:

<?xml version="1.0" encoding="utf-8"?>

It's minor, but it helps to make TinyXml's output
exactly the same as most other serializers which is useful in version control situations (e.g. when
switching to TinyXml).

-Wade