Fix very slow sorting of the status field.
Fix very slow sorting of the status field.

svn path=/trunk/kdenetwork/kmail/; revision=160854

lefou/kdepim-noakonadi,lefou/kdepim-noakonadi,lefou/kdepim-noakonadi,lefou/kdepim-noakonadi,lefou/kdepim-noakonadi,lefou/kdepim-noakonadi