Clearing GtkComboBoxEntry

[Steve Harrington <steven harrington verizon net>]

I have an application using GtkComboBoxEntry with a simple 2-column 
int/char * ListEntry model.  If the user enters data in the box (as 
opposed to using a pull-down selector) I can access the index with
      gtk_combo_box_get_active( GTK_COMBO_BOX(W) );
and the text with
      gtk_combo_box_get_active_text (GTK_COMBO_BOX(W));

The index is -1 as expected and the text is the text that what was entered.
The question is:  How do I clear the text field when I have finished 
with it.
From the FAQ and other documentation it seems that I should be able to 
access the actual GtkEntry widget within the GtkComboBoxEntry widget, 
get the GtkEntryBuffer, and clear it with 
gtk_entry_buffer_delete_text().  None of these buffer functions/headers 
are marked as depreciated but also none of them are my version of the 
gtk headers (/usr/include/gtk-2.0/gtk/gtkentry.h) or anywhere else in 
the gtk headers.