#30 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" ?>

With this patch, you get:

<?xml version="1.0"?>

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 Brainerd]

Patch file tinyxml.cpp.