Mark some tests as expensive

Mark some tests as expensive

* test/lisp/autorevert-tests.el
(auto-revert-test00-auto-revert-mode)
(auto-revert-test03-auto-revert-tail-mode)
(auto-revert-test04-auto-revert-mode-dired):
* test/lisp/cedet/semantic-utest-c.el
(semantic-test-c-preprocessor-simulation):
* test/lisp/cedet/srecode-utest-getset.el
(srecode-utest-getset-output):
* test/lisp/emacs-lisp/cl-seq-tests.el (cl-seq-test-bug24264):
* test/lisp/emacs-lisp/package-tests.el
(package-test-update-archives-async):
* test/lisp/filenotify-tests.el (file-notify-test03-events)
(file-notify-test04-autorevert)
(file-notify-test05-file-validity, file-notify-test08-backup):
* test/lisp/net/gnutls-tests.el (test-gnutls-005-aead-ciphers):
* test/lisp/shadowfile-tests.el (shadow-test00-clusters)
(shadow-test09-shadow-copy-files):