Derive Man and WoMan modes from special-mode

Derive Man and WoMan modes from special-mode

* lisp/man.el (Man-mode-map): Set parent to map composed from both
button-buffer-map and special-mode-map.  Remove redundant bindings.
Fix menu to refer to the quit-window command.
(Man-mode): Derive from special-mode.  Fix docstring.  Remove redundant
buffer-read-only binding.
(Man-quit): Remove.
* lisp/woman.el (woman-really-find-file): Use setq-local.
(woman-mode-map): Refer to woman-mode in docstring.
(woman-mode): Derive from special-mode.  Document woman-mode-map in
docstring.  Use setq-local where possible; imenu-generic-expression is
already buffer-local.
(woman-negative-vertical-space): Replace unused binding with _.