When literal mode is entered it should exit automatically when the
matching close tag of the last unclosed open tag is encountered. This
patch fixes this.
The main incompatibility is that the error reporting method is now
called as
parser.syntax_error(msg)
instead of
parser.syntax_error(lineno, msg)
This new version also has some code to deal with the <?xml?> and
<!DOCTYPE> tags at the start of an XML document.
The documentation has been updated, and a small test module has been
created.
