Display a more informative error message in the case the server doesn't support the TOP command and the user doesn't want to fetch big mails immediately.
Display a more informative error message in the case the server doesn't
support the TOP command and the user doesn't want to fetch big mails
immediately.

svn path=/trunk/kdenetwork/kmail/; revision=126585

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