fix: OverlayWatched alignment on select

When view is Thumbnails and file is selected/unselected the overlay
horizontal alignment is off and looks funky.
this fixes that.
[osx/docs] - update README.osx - we support building with Xcode 5.1.1 on Mavericks 10.9.x against SDK 10.8 and 10.9
[infomanager] turns out listitem properties are case insensitive. fixes missing fanart on some skins.

We store properties we're looking up in CGUIInfoManager::m_listItemProperties case sensitive, but the map in CGUIListItem is
handled case-insensitive.
Merge pull request #4939 from uNiversaI/overlayfix

fix: Cosmetic OverlayWatched alignment on select