[0.85] lighter backtrace output / hide / skip some stuff

git-svn-id: https://forge.indepnet.net/svn/glpi/branches/0.85-work@20806 35612d4c-9d10-0410-837c-bf9dd1be60d7
[0.85] minor clean

git-svn-id: https://forge.indepnet.net/svn/glpi/branches/0.85-work@20807 35612d4c-9d10-0410-837c-bf9dd1be60d7