Tab bar item is selected even when tab bar view item is prevented from being selected.

[chinhster]

If your delegate prevents a tab view item from being selected with the method [NSTabViewDelegate tabView:shouldSelectTabViewItem:], the tab view selection doesn't change but the tab bar selection does.

To fix this, I had to modify mouseDown: method in MMAttachedTabBarButton.m to not change the state of the previous selected button and the button that was just clicked (PSMTabBarControl doesn't change the state but relies on selectTabViewItem: to do it).