Sets @label as the label used for the tool button. The #GtkToolButton:label
property only has an effect if not overridden by a non-%NULL
#GtkToolButton:label-widget property. If both the #GtkToolButton:label-widget
and #GtkToolButton:label properties are %NULL, the label is determined by the
#GtkToolButton:stock-id property. If the #GtkToolButton:stock-id property is
also %NULL, @button will not have a label.
Sets @label as the label used for the tool button. The #GtkToolButton:label property only has an effect if not overridden by a non-%NULL #GtkToolButton:label-widget property. If both the #GtkToolButton:label-widget and #GtkToolButton:label properties are %NULL, the label is determined by the #GtkToolButton:stock-id property. If the #GtkToolButton:stock-id property is also %NULL, @button will not have a label.