Previously, these scripts could run before all the Eshell modules had
fully-initialized.
* lisp/eshell/esh-mode.el (eshell-after-initialize-hook): New hook...
(eshell-mode): ... run it.
* lisp/eshell/em-script.el (eshell-run-startup-scripts): New function...
(eshell-script-initialize): ... add it to
'eshell-after-initialize-hook'.
* etc/NEWS: Announce 'eshell-after-initialize-hook'.