Nudge WoMan toward lexical-binding

Nudge WoMan toward lexical-binding

* lisp/woman.el (woman-parse-man.conf, woman-manpath-add-locales):
Use cl-pushnew instead of add-to-list.
(woman-justify-list): Rename to woman-justify-styles.
(woman-justify-styles): New array.
(woman-justify, woman-decode-region, woman2-ad, woman2-na): Use it.
(woman-cached-data): Use cl-pushnew instead of add-to-list.