Obsolete dired-x's directory local variables in favor of standard ones.

Obsolete dired-x's directory local variables in favor of standard ones.

* lisp/dired.el (dired-mode): Call hack-dir-local-variables-non-file-buffer.

* lisp/dired-x.el (dired-omit-mode): Safe if boolean.
(dired-enable-local-variables): Fix doc and custom type.  Mark risky.
(dired-enable-local-variables, dired-local-variables-file)
(dired-hack-local-variables): Make obsolete.
(dired-omit-here-always): Use dir-locals.el instead.

* doc/misc/dired-x.texi (Features): Don't advertise obsolete local variables.
Simplify layout.
(Omitting Variables): Update local variables example.
(Local Variables): Say this is obsolete.  Fix description of
dired-enable-local-variables possible values.

* etc/NEWS: Relocate the existing entry about directory local
variables in file-les buffers, and make it clearer.
Mention above dired changes.