Not deleted, because it's the only option for some other operating
systems such as FreeBSD or any other slightly exotic operating
system someone might try and run dolphin on.
Dolphin code already builds against SDL2 but the build system never
checks for SDL2, which is the what latest SDL is called now. SDL2
replaces SDL 1.3. This allows Dolphin to be build against SDL2, which
activates certain new features such as the haptic interface.