Incorrect declaration of virtual function makes project not compilable with float type

https://github.com/flexible-collision-library/fcl/blob/ff8324929fdf76d6646d7b90c221a6a5bda438d8/include/fcl/math/motion/interp_motion.h#L79

This bug prevents building FCL types with float. Declaration of this function should not take double as argument, but templated type S.