RobExtremes: bug in (population) variance of GEV xi=0 discovered

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/robast@743 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
RobExtremes:: yet two more fixes

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/robast@744 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
RobExtremes fixed the problem with inadmissible return values of MLE

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/robast@745 edb9625f-4e0d-4859-8d74-9fd3b1da38cb