gtk_window_set_title function

[Rob Huffstedtler <rob bagpipe com>]

Looking through the Freeciv source, I came across the following:

  gtk_window_set_title (GTK_WINDOW (toplevel), _("Freeciv"));

What is the purpose of the underbar?  I checked the tutorial, the RDP, and
Harlow and no one seems to mention this.  I tried it in a small test app
and it throws an error.

Thanks

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