ui-calendar: Use scroll window implementation

Make use of the generic scroll window implementation for the calendar
view. Note that this is useful despite the panel not needing a scroll
bar, since the scroll window functions can be used to draw the panel
border and take care of relative positions.

Signed-off-by: Lukas Fleischer <calcurse@cryptocrack.de>

src/ui-todo.c

@@ -53,7 +53,6 @@ void ui_todo_add(void)
 			ch = wgetch(win[KEY].p);
 		}
 		todo_add(todo_input, ch - '0', NULL);
-		ui_todo_sel_move(1);
 		ui_todo_load_items();
 	}
 }