GtkComboBoxEntry just displaying strings. If you use this function to
create a text combo box, you should only manipulate its data source with
the following convenience functions: gtkComboBoxAppendText,
gtkComboBoxInsertText, gtkComboBoxPrependText and
gtkComboBoxRemoveText.gtkComboBoxEntryNewText()GtkWidget] A new text GtkComboBoxEntry.