Could you add this to glib, please?

[Anthony Graphics <agl sheba sequoiap com>]

void
g_string_vprintf (GString     *string,
		       const gchar *fmt,
		       va_list      args)
{
  gchar *buffer;

  buffer = g_strdup_vprintf (fmt, args);
  g_string_assign (string, buffer);
  g_free (buffer);
}