Bindat: Document `sint`; add `le` arg to `uint`; deprecate `uintr`

Bindat: Document `sint`; add `le` arg to `uint`; deprecate `uintr`

* lisp/emacs-lisp/bindat.el (bindat--type) <uint>: Add `le` optional arg.
(bindat--type) <uintr>: Delete method.
(uintr): Re-define as a bindat-macro instead.
(bindat-type): Update docstring accordingly.
(bindat--primitives): Update.
(sint): Simplify.

* doc/lispref/processes.texi (Bindat Types): Update `uint`, add `sint`,
and remove `uintr`.

* test/lisp/emacs-lisp/bindat-tests.el (data-bindat-spec): Use the new
`le` arg of `uint` instead of `uintr`.