Corrected underlying name for getPPP
Resolved 3p optimization bug which permitted NaN's to appear in output.  These are now trapped and warned regarding failure to converge.

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/abernethy@103 edb9625f-4e0d-4859-8d74-9fd3b1da38cb