FastXML doesn't parse attributes with legally unescaped single and double quote characters

In XML, single or double quotes can be used to surround an attribute value. Furthermore, it is legal to use whichever character isn't chosen within that attribute value without escaping it. Currently, we don't ensure the closing character is the same as the opening, leading to errors when parsing some valid XML files.

1. Create an XML with an attribute containing single or double quotes

   <tag attr="test's"/>
   

2. Parse your XML using the FastXML parser
3. Observe that errors are returned due to the attribute being closed on the single quote (apostrophe) character instead of the double quote