Dev fix - Full backwards compatiblity with fnServerParams with array
syntax paraneter names

- Data added using fnServerParams with array syntax had different
  behaviour in 1.10 from 1.9. In 1.9 jQuery would create an array for
  us, but in 1.10 before we create an object first, we need to create
  that array ourselves. So the following code had different behaviour:

		"sAjaxSource": "data/arrays.txt",
		"fnServerParams": function ( d ) {
			d.push(
				{name: 'somekey[]', value: 'somevalue1'},
				{name: 'somekey[]', value: 'somevalue2'}
			);
		}

In 1.10 it would have sent `somekey[] = somevalue2` but 1.9 would have
sent both as part of an array.

To maintain full compatiblity with 1.9 we need to convert this syntax to
an array - this commit does that.

I was concerned about using parameters in the brackets, but jQuery only
searches for `[]` when performing this conversion. We could use $.param
and then decode the created query string, which would be absolutely 100%
comaptible, but would involve additional code and I think this method
provides that 100% compatiblity from reading the jQuery code), and its
shorter.