mpspline: changed documentation to indicate that soil profiles with 1 observed horizon can be accepted by the function

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/gsif@171 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
mpspline: made adjustments to ensure function better handles soil profiles with 1 horizon

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/gsif@172 edb9625f-4e0d-4859-8d74-9fd3b1da38cb