This function will generate a button click in the upwards or downwards
spin button arrow areas, usually leading to an increase or decrease of
spin button's value.
Usage
gtkTestSpinButtonClick(spinner, button, upwards)
Arguments
spinner
valid GtkSpinButton widget.
button
Number of the pointer button for the event, usually 1, 2 or 3.
upwards
TRUE for upwards arrow click, FALSE for downwards arrow click.