Make byte-compiler warn about wide docstrings

Make byte-compiler warn about wide docstrings

* lisp/emacs-lisp/bytecomp.el (byte-compile--wide-docstring-p):
(byte-compile-docstring-length-warn): New defuns.
(byte-compile-docstring-max-column): New defcustom.
(byte-compile--wide-docstring-substitution-len): New variable.
(byte-compile-warning-types, byte-compile-warnings): New value
'docstrings'.
(byte-compile-file-form-autoload, byte-compile-file-form-defvar):
(byte-compile-file-form-defvar-function, byte-compile-lambda):
(byte-compile-defvar, byte-compile-file-form-defalias): Warn about too
wide docstrings.  (Bug#44858)

* test/lisp/emacs-lisp/bytecomp-tests.el
(bytecomp-warn-wide-docstring/defconst)
(bytecomp-warn-wide-docstring/defvar): New tests.
(bytecomp--define-warning-file-test): New macro.
(bytecomp/warn-wide-docstring-autoload\.el)
(bytecomp/warn-wide-docstring-custom-declare-variable\.el)
(bytecomp/warn-wide-docstring-defalias\.el)
(bytecomp/warn-wide-docstring-defconst\.el)
(bytecomp/warn-wide-docstring-define-abbrev-table\.el)
(bytecomp/warn-wide-docstring-define-obsolete-function-alias\.el)
(bytecomp/warn-wide-docstring-define-obsolete-variable-alias\.el)
(bytecomp/warn-wide-docstring-defun\.el)
(bytecomp/warn-wide-docstring-defvar\.el)
(bytecomp/warn-wide-docstring-defvaralias\.el)
(bytecomp/warn-wide-docstring-ignore-fill-column\.el)
(bytecomp/warn-wide-docstring-ignore-override\.el)
(bytecomp/warn-wide-docstring-ignore\.el)
(bytecomp/warn-wide-docstring-multiline-first\.el)
(bytecomp/warn-wide-docstring-multiline\.el): New tests.
* test/lisp/emacs-lisp/bytecomp-resources/warn-wide-docstring-autoload.el:
* test/lisp/emacs-lisp/bytecomp-resources/warn-wide-docstring-custom-declare-variable.el:
* test/lisp/emacs-lisp/bytecomp-resources/warn-wide-docstring-defalias.el:
* test/lisp/emacs-lisp/bytecomp-resources/warn-wide-docstring-defconst.el:
* test/lisp/emacs-lisp/bytecomp-resources/warn-wide-docstring-define-abbrev-table.el:
* test/lisp/emacs-lisp/bytecomp-resources/warn-wide-docstring-define-obsolete-function-alias.el:
* test/lisp/emacs-lisp/bytecomp-resources/warn-wide-docstring-define-obsolete-variable-alias.el:
* test/lisp/emacs-lisp/bytecomp-resources/warn-wide-docstring-defun.el:
* test/lisp/emacs-lisp/bytecomp-resources/warn-wide-docstring-defvar.el:
* test/lisp/emacs-lisp/bytecomp-resources/warn-wide-docstring-defvaralias.el:
* test/lisp/emacs-lisp/bytecomp-resources/warn-wide-docstring-ignore-fill-column.el:
* test/lisp/emacs-lisp/bytecomp-resources/warn-wide-docstring-ignore-override.el:
* test/lisp/emacs-lisp/bytecomp-resources/warn-wide-docstring-ignore.el:
* test/lisp/emacs-lisp/bytecomp-resources/warn-wide-docstring-multiline-first.el:
* test/lisp/emacs-lisp/bytecomp-resources/warn-wide-docstring-multiline.el:
New files.