bezier interpolation fixed


git-svn-id: svn://svn.code.sf.net/p/qwt/code/trunk@1840 29e17f8d-cf37-471e-a288-72cc03a76eda
temporarily a Bezier1 fit mode added


git-svn-id: svn://svn.code.sf.net/p/qwt/code/trunk@1841 29e17f8d-cf37-471e-a288-72cc03a76eda
using Bezier for spline curve fitting, legacy code moved to QwtSpline


git-svn-id: svn://svn.code.sf.net/p/qwt/code/trunk@1842 29e17f8d-cf37-471e-a288-72cc03a76eda