Fritsch-Butland interpolation added


git-svn-id: svn://svn.code.sf.net/p/qwt/code/trunk@1867 29e17f8d-cf37-471e-a288-72cc03a76eda
splineeditor example improved


git-svn-id: svn://svn.code.sf.net/p/qwt/code/trunk@1868 29e17f8d-cf37-471e-a288-72cc03a76eda
harminic spline instead of Fritsch/Butler


git-svn-id: svn://svn.code.sf.net/p/qwt/code/trunk@1869 29e17f8d-cf37-471e-a288-72cc03a76eda
alternative algo added


git-svn-id: svn://svn.code.sf.net/p/qwt/code/trunk@1870 29e17f8d-cf37-471e-a288-72cc03a76eda
loops improved


git-svn-id: svn://svn.code.sf.net/p/qwt/code/trunk@1871 29e17f8d-cf37-471e-a288-72cc03a76eda
code simplified


git-svn-id: svn://svn.code.sf.net/p/qwt/code/trunk@1872 29e17f8d-cf37-471e-a288-72cc03a76eda