RobExtremes: ...yet another time played around the search interval for sigma in startEstGEV.R

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/robast@737 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
RobExtremes: packed startEstGEV.R into a try-catch...

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/robast@738 edb9625f-4e0d-4859-8d74-9fd3b1da38cb