Improve toggleClass

[soywiz]

toggleClass: function( classNames, set ) {

if (set === undefined) set = jQuery.className.has( this, classNames ); jQuery.className[ set ? "add" : "remove" ]( this, classNames );

}

It will allow to do something like this, while mantaining the original behaviour:

$('#id').toggleClass('enabled', (var > 0));

[flesler]

Duplicate of #1681.