Add cl-with-accessors

Add cl-with-accessors

* lisp/emacs-lisp/cl-macs.el (cl-with-accessors): New macro.
* doc/misc/cl.texi (Structures): Mention the new macro.
* test/lisp/emacs-lisp/cl-macs-tests.el (cl-lib-struct-with-accessors):
New Test.
* etc/NEWS (New macro 'cl-with-accessors'.): Mention the macro.

This macro is useful when making repeated use of a structures accessor
functions, such as reading from a slot and then writing to a slot.  It
is similar to 'with-slots' from EIEIO, but uses accessor functions
instead of slot names.

(cherry picked from commit e04d1dafc700813c835ae4e45af4e104c49e8875)