Creates a menu item which has two states, on or off, represented by a check mark with a text label specified by label. If label is NULL or not specified then no label is created. If label contains underscore characters then the character following the underscore will be underlined and the character following the first underscore will be used as the mnemonic keyboard accelerator. The use_underline parameter defaults to TRUE. If use_underline is set to FALSE the label text will not be parsed for mnemonic characters.