|Changes or indicates the checked state of a
checkable menu item.
VarioMenuItem.Checked = boolean
boolean - When is true the menu item is checked and a
tick appears on the left of the caption, when false - it is unchecked.
Checked property is valid only for menu items which has their Type set to mitCheckable or for
radio group members.
When AutoCheck property is set to true
Checked value is updated automatically to indicate the new item state before the execution
of the click function. Thus the menu handler can read the current state from it. This
applies both to checkable and radio group member items.