Converts an XML document that is represented as a string 
variable into an XML document object.
xmlParse(xmlString [, caseSensitive] [, validator]) → returns xml
Any of the following: 
- A string containing XML text. 
- The name of an XML file. 
- The URL of an XML file; valid protocol identifiers 
include http, https, ftp, and file.
Any of the following: 
- The name of a Document Type Definition (DTD) or 
XML Schema file. 
- The URL of a DTD or Schema file; valid protocol 
identifiers include http, https, ftp, and file. 
- A string representation of a DTD or Schema. 
- An empty string; in this case, the XML file must 
contain an embedded DTD or Schema identifier, which 
is used to validate the document.