Add error location properties to parser error

[marekweb]

Currently when there's a parser error, the location of the error is appended as a string to the error message.

Error: Unexpected close tag
Line: 0
Column: 17
Char: >

It would be useful to provide the location as a set of properties on the object.

{
  line: 0,
  column: 17,
  char: '>'
}

Use cases:

Better error reporting. Allow the possibility of excerpting the XML input to show the location of the error.

parser.onerror = function(error) {
  console.error('Parsing error at location: ' + error.line + ':' + error.column)
}