added function spsample.prob

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/gsif@164 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
added corrections in mpspline.R by Brandon Malone

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/gsif@165 edb9625f-4e0d-4859-8d74-9fd3b1da38cb