SDL_SYS_Haptic* link errors on iOS

I am getting multiple link errors related to SDL_SYS_Haptic* when building
my application on iOS.

I compiled SDL2 using premake/Xcode-iOS/SDL2/SDL2.xcodeproj. It appears
that this project does not contain a SDL_syshaptic.c implementation.

Adding src/haptic/dummy/SDL_syshaptic.c to the project manually fixes the
link errors.

This was tested with hg 8692:715d401184a2