Cleanup some type predicates

Cleanup some type predicates

Use the new `cl--define-built-in-type` to reduce the manually
maintained list of built-in type predicates.
Also tweak docstrings to use "supertype" rather than "super type",
since it seems to be what we use elsewhere.

* lisp/subr.el (special-form-p): Remove redundant `fboundp` test.
(compiled-function-p): Don'Return nil for subrs that aren't functions.

* lisp/emacs-lisp/cl-macs.el (type predicates): Trim down the list.

* lisp/emacs-lisp/cl-preloaded.el (cl--define-built-in-type):
Register the corresponding predicate if applicable.
(atom, null): Specify the predicate name explicitly.