* lisp/textmodes/ispell.el: Compile with lexical-binding

* lisp/textmodes/ispell.el: Compile with lexical-binding

(declare-function): Don't define any more.
(ispell-check-minver, ispell-looking-back): Tweak definition so that
the compiler can obviously know that it's always defined.
(ispell-debug-buffer): Declare var.
(ispell-hunspell-fill-dictionary-entry)
(ispell-parse-hunspell-affix-file, ispell-hunspell-add-multi-dic)
(ispell-find-hunspell-dictionaries, ispell-set-spellchecker-params)
(ispell-command-loop): Avoid add-to-list on local variables.