splines again


git-svn-id: svn://svn.code.sf.net/p/qwt/code/trunk@1927 29e17f8d-cf37-471e-a288-72cc03a76eda
QwtSpline, QwtSplineCubic, QwtSplineLocal


git-svn-id: svn://svn.code.sf.net/p/qwt/code/trunk@1928 29e17f8d-cf37-471e-a288-72cc03a76eda