* lisp/eshell/em-hist.el: Stop requiring 'eshell' and 'em-pred'
(extension modules shouldn't require each other so they can be
independent).
(eshell-hist-parse-modifier): Ensure this can only be called when
'em-pred' is in use, and declare the relevant function.
* lisp/eshell/eshell.el (eshell-non-interactive-p): Move from here...
* lisp/eshell/esh-mode.el (eshell-non-interactive-p): ... to here.