Merge missing commit from emacs-25 branch

Merge missing commit from emacs-25 branch

* test/Makefile.in (SELECTOR_DEFAULT, SELECTOR_EXPENSIVE, SELECTOR):
New variables.
(check-expensive, check-doit): New targets.

* Makefile.in (check-expensive): New target.

* test/lisp/autorevert-tests.el
(auto-revert-test01-auto-revert-several-files):
* test/lisp/filenotify-tests.el (file-notify--deftest-remote)
(file-notify-test06-many-events):
* test/lisp/net/tramp-tests.el (tramp-test26-process-file)
(tramp-test27-start-file-process, tramp-test28-shell-command)
(tramp-test29-vc-registered)
(tramp-test31-special-characters-with-stat)
(tramp-test31-special-characters-with-perl)
(tramp-test31-special-characters-with-ls)
(tramp-test32-utf8-with-stat, tramp-test32-utf8-with-perl)
(tramp-test32-utf8-with-ls, tramp-test33-asynchronous-requests)
(tramp-test35-unload): Tag the tests as :expensive-test.