(trunk gtk) make "gtr_label_set_text" public and use it everywhere instead of gtk_lab...

(trunk gtk) make "gtr_label_set_text" public and use it everywhere instead of gtk_label_set_text()

Some of the refresh events to the main window's torrent list are caused by main window relayout caused by the toolbar's GtkLabels recalculating their size after being updated once per second. To prevent relayout in some trivial cases, I'm replacing the gtk_label_set_text() calls with gtr_label_set_text() because the latter doesn't update the label widget if the old and new text strings are the same.

There are other changes that can handle more important cases -- I'll test those out next.