cl-typep: Emit warning when using a type not known to be a type

cl-typep: Emit warning when using a type not known to be a type

`cl-typep` has used a heuristic that if there's a `<foo>-p` function,
then <foo> can be used as a type.  This made sense in the past where
most types were not officially declared to be (cl-)types, but nowadays
this just encourages abuses such as using `cl-typecase` with
"types" like `fbound`.  It's also a problem for EIEIO objects, where
for historical reasons `<foo>-p` tests if the object is of type
exactly `<foo>` whereas (cl-typep OBJ <foo>) should instead test
if OBJ is a *subtype* of `<foo>`.

So we change `cl-typep` to emit a warning whenever this "-p" heuristic
is used, to discourage abuses, encourage the use of explicit
`cl-deftype` declarations, and try and detect some misuses of
`<foo>-p` for EIEIO objects.

* lisp/emacs-lisp/eieio.el (defclass): Define as type not only at
run-time but also for the current compilation unit.

* lisp/emacs-lisp/eieio-core.el (class, eieio-object): Define as types.

* lisp/emacs-lisp/cl-preloaded.el (cl-struct-define): Don't abuse the
"-p" heuristic.

* lisp/emacs-lisp/cl-macs.el (cl-deftype-satisfies):
Add entries for frames, windows, markers, and overlays.
(cl-typep): Emit a warning when using a predicate that is not known to
correspond to a type.

* lisp/files.el (file-relative-name): Fix error that can trigger if
there's an(other) error between loading `files.el` and loading
`minibuffer.el`.