* lisp/eshell/esh-opt.el: Fix last change to set lexical-vars properly.

* lisp/eshell/esh-opt.el: Fix last change to set lexical-vars properly.
(eshell--do-opts): Rename from eshell-do-opt, remove arg `body-fun',
return args and options.
(eshell-eval-using-options): Use the new return value of
eshell--do-opts to set the options's vars in their scope.
(eshell--set-option): Rename from eshell-set-option.
Add arg `opt-vals'.
(eshell--process-option): Rename from eshell-process-option.
Add arg `opt-vals'.
(eshell--process-args): Use an `opt-vals' alist to store the options's
values during their processing and return them additionally to the
remaining args.

Fixes: debbugs:15379