fix mysql extension usage for install


git-svn-id: https://forge.indepnet.net/svn/glpi/trunk@20491 35612d4c-9d10-0410-837c-bf9dd1be60d7
complete last


git-svn-id: https://forge.indepnet.net/svn/glpi/trunk@20492 35612d4c-9d10-0410-837c-bf9dd1be60d7