Backport kqueue integration from master

Backport kqueue integration from master

* configure.ac (--with-file-notification): Add kqueue.
(top): Remove special test for "${HAVE_NS}" and
${with_file_notification}, this is handled inside gfilenotify
tests.  Add kqueue tests.  Use NOTIFY_CFLAGS and NOTIFY_LIBS
instead of library specific variables.  Add error message for
gfile on Nextstep.

* doc/lispref/os.texi (File Notifications): Add kqueue as backend.
Fix some glitches in the example.

* etc/NEWS: Mention kqueue.

* lisp/filenotify.el (file-notify--library)
(file-notify-descriptors, file-notify-callback)
(file-notify-add-watch, file-notify-rm-watch)
(file-notify-valid-p): Add kqueue support.
(file-notify--rm-descriptor): Remove WHAT arg.

* src/Makefile.in: Use NOTIFY_CFLAGS and NOTIFY_LIBS.

* src/emacs.c (main): Call globals_of_kqueue and syms_of_kqueue.

* src/inotify.c (inotifyevent_to_event): Extract file name from
watch_object if the event doesn't provide it.
(Finotify_add_watch): Add file name to watch_object.

* src/keyboard.c (make_lispy_event): Check also for HAVE_KQUEUE.

* src/kqueue.c: New file.

* src/lisp.h: Declare extern globals_of_kqueue and syms_of_kqueue.

* test/automated/file-notify-tests.el
(file-notify--test-expected-events): Remove.
(file-notify--test-cleanup): Do not set that variable.
(file-notify--test-timeout) Use different timeouts for
different libraries.
(file-notify--test-library): New defun.
(file-notify--test-event-test): Make stronger checks.
(file-notify--test-with-events): EVENTS can also be a list of
lists.  Flush outstanding events before running the body.
Make timeout heuristically depend on the number of events.
(file-notify-test01-add-watch, file-notify-test02-events)
(file-notify-test04-file-validity, file-notify-test05-dir-validity):
Rewrite in order to call file monitors but directory monitors.
(file-notify-test02-events, file-notify-test04-file-validity): Do
not skip cygwin tests.  Add additional test for file creation.
Adapt expected result for different backends.
(file-notify-test03-autorevert): Some of the tests don't work for
w32notify.
(file-notify-test06-many-events): New test.