* lisp/eshell/em-pred.el: Take advantage of lexical scoping

* lisp/eshell/em-pred.el: Take advantage of lexical scoping

Also remove redundant `:group` arguments.

(eshell-parse-modifiers): Make sure we pass a function value.
(eshell-parse-arg-modifier, eshell-parse-modifiers)
(eshell-add-pred-func, eshell-pred-user-or-group)
(eshell-pred-file-time, eshell-pred-file-type, eshell-pred-file-mode)
(eshell-pred-file-links, eshell-pred-file-size)
(eshell-pred-substitute, eshell-include-members, eshell-join-members)
(eshell-split-members): Use proper closures.