reduced option "digits" from 5 to 3 to reduce the chance of getting differences in the output file on different computers

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/sampleselection@1548 d36ae590-6c38-44c5-9ba5-7217e93607d8
added tests for lrtest() applied to selection (tobit-2) models

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/sampleselection@1549 d36ae590-6c38-44c5-9ba5-7217e93607d8