When has-entry is TRUE, GtkComboBox already adds a cell renderer
for the text column, so avoid adding a second one in GtkComboBoxText.
https://bugzilla.gnome.org/show_bug.cgi?id=632381
(cherry picked from commit b613cc64786a95ea069d3d308906133165062315)
This is a derived class of GtkComboBox to replace the
gtk_combo_box_*_text() convenience API.
Fixes https://bugzilla.gnome.org/show_bug.cgi?id=612396
Signed-off-by: Javier Jardón <jjardon@gnome.org>
(cherry picked from commit 7a5a5e9c5dee16601c8bf1df67ce12c81000bfb9)