[Cleaning] removed all warnings

include/spline/bernstein.h

include/spline/bezier_curve.h

include/spline/bezier_polynom_conversion.h

include/spline/curve_abc.h

include/spline/exact_cubic.h

include/spline/helpers/effector_spline.h

include/spline/helpers/effector_spline_rotation.h

include/spline/polynom.h

include/spline/spline_deriv_constraint.h

src/tests/spline_test/Main.cpp