bug#22792: eshell-mode-map declaration

[Alex Branham]

I can work on this bug. Moving the (re)-definition of eshell-mode-map
out of eshell-mode is easy enough. The tricky part is that some of
eshell's modules (e.g. em-cmpl) use define-key in eshell-mode-map (or
eshell-command-map) too. This results in those keys getting redefined
each time eshell is invoked.

How do people want to handle that? We could create an em-cmpl minor mode
with its own keymap, I suppose. Would that be satisfactory?

Thanks,
Alex