* configure.ac (file-notification): New option, replaces inotify option.

* configure.ac (file-notification): New option, replaces inotify option.
(HAVE_W32): Remove w32notify.o.
(with_file_notification): Add checks for glib and w32. Adapt check
for inotify.
(Summary): Add entry for file notification.

* autogen/config.in: Add entries for HAVE_GFILENOTIFY,
HAVE_W32NOTIFY and USE_FILE_NOTIFY.

* lisp/autorevert.el (auto-revert-notify-enabled)
(auto-revert-notify-rm-watch, auto-revert-notify-add-watch)
(auto-revert-notify-event-p, auto-revert-notify-event-file-name)
(auto-revert-notify-handler): Handle also gfilenotify.

* lisp/subr.el: (file-notify-handle-event): New defun. Replacing ...
(inotify-event-p, inotify-handle-event, w32notify-handle-event):
Removed.

* src/Makefile.in (NOTIFY_OBJ): New variable.
(base_obj): Replace inotify.o by $(NOTIFY_OBJ).

* src/emacs.c (main): Use HAVE_W32NOTIFY to wrap respective code.
Call syms_of_gfilenotify.

* src/gfilenotify.c: New file.

* src/keyboard.c (Qfile_notify): New variable.  Replaces Qfile_inotify
and Qfile_w32notify.
(top): Wrap respective code by HAVE_GFILENOTIFY, HAVE_INOTIFY,
HAVE_W32NOTIFY and USE_FILE_NOTIFY.

* src/lisp.h: Declare syms_of_gfilenotify.

* src/termhooks.h (e): Wrap enum by USE_FILE_NOTIFY.