Add option to prevent text selection

[mar10]

When right-clicking a div-tag the contained text sometimes is marked as selected by the browser. (Observed with Safari on a MacBook, using two-finger click on the trackpad).

An option disableSelection: true could help to prevent this.

jQuery UI implemented it this way (note: this function is deprecated since 1.9):

$.support.selectstart = "onselectstart" in document.createElement( "div" );
$.fn.extend({
    disableSelection: function() {
        return this.bind( ( $.support.selectstart ? "selectstart" : "mousedown" ) +
            ".ui-disableSelection", function( event ) {
                event.preventDefault();
            });
    },

    enableSelection: function() {
        return this.unbind( ".ui-disableSelection" );
    },