starting with cardinal splines


git-svn-id: svn://svn.code.sf.net/p/qwt/code/trunk@1933 29e17f8d-cf37-471e-a288-72cc03a76eda
spline classes reorganized


git-svn-id: svn://svn.code.sf.net/p/qwt/code/trunk@1934 29e17f8d-cf37-471e-a288-72cc03a76eda