Fix link error in iOS examples
Fix link error like the following when building the iOS examples:
Undefined symbols for architecture x86_64:
"vtkInteractorStyleMultiTouchCamera::New()", referenced from:
-[MyGLKViewController setupPipeline] in MyGLKViewController.o
ld: symbol(s) not found for architecture x86_64
Because the examples use vtkInteractorStyleMultiTouchCamera, the InteractionStyle module must be enabled.