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.