Some inotify cleanup

Some inotify cleanup

This catches some problems with integer overflow and races
that I noticed in inotify.c after reviewing the changes
installed to fix Bug#26126.
* src/fns.c, src/lisp.h (equal_no_quit): Now extern.
* src/inotify.c (aspect_to_inotifymask):
Check for cycles and for improper lists.
(make_lispy_mask, lispy_mask_match_p): Remove.
All callers changed to use INTEGER_TO_CONS and CONS_TO_INTEGER.
(inotifyevent_to_event, add_watch):
Don’t assume watch descriptors and cookies fit in fixnums.
(add_watch): Use assoc_no_quit, not Fassoc.
Avoid integer overflow in (very!) long-running processes where
the Emacs watch ID could overflow.  Avoid some duplicate code.
(find_descriptor): New function.
(remove_descriptor): First arg is now the returned value from
find_descriptor, rather than the descriptor.  This way, the
value can be removed without calling Fdelete, which might quit.
Wait until the end (when watch_list is consistent) before signaling
any errors.
(remove_watch, inotify_callback):
Use find_descriptor to avoid the need for Fdelete.
(inotify_callback): Use simpler tests for ioctl failure.
Free temporary buffer if signaled, and put it on the stack if small.
Use ssize_t to index through read results, to avoid a cast.
(valid_watch_descriptor): New function, with a tighter check.
(Finotify_rm_watch, Finotify_valid_p): Use it.
(Finotify_valid_p): Use assoc_no_quit and ass_no_quit instead
of Fassoc.  Do not assume the first assoc succeeds.
* test/src/inotify-tests.el (inotify-valid-p-simple):
Add inotify-valid-p tests, some of which dump core without
the fixes noted above.