Hello,

The attached patch adds the macro `cl-with-accessors'.  This macro uses 
`cl-symbol-macrolet' to treat a symbol like a use of an accessor 
function, such as those made by `cl-defstruct' and `cl-defclass'. This 
can be helpful when using repeated calls to read and write with the 
functions.

It is based on the description at
https://www.lispworks.com/documentation/HyperSpec/Body/m_w_acce.htm

Also, in the test `cl-lib-struct-accessors' in 
test/lisp/emacs-lisp/cl-lib-tests.el, it checks for the keyword 
`:readonly', but the documented keyword is `:read-only'.  Is this a 
typo, or was this intentional?

Thank you.