missing copyrights added


git-svn-id: svn://svn.code.sf.net/p/qwt/code/trunk@2050 29e17f8d-cf37-471e-a288-72cc03a76eda
OpenGL dependeny added to qwt.prf


git-svn-id: svn://svn.code.sf.net/p/qwt/code/trunk@2052 29e17f8d-cf37-471e-a288-72cc03a76eda
points changed for parametric splines


git-svn-id: svn://svn.code.sf.net/p/qwt/code/trunk@2053 29e17f8d-cf37-471e-a288-72cc03a76eda