can't bind control-z in 21.5, but in 21.4 I can

[Stephen J. Turnbull]

Uwe Brauer writes:
 > 
 > Neither of the following binding 
 > (global-set-key [(control z)]   'suspend-emacs-or-iconify-frame)
 > (global-set-key "\C-z"   'suspend-emacs-or-iconify-frame)
 > works, 
 > 
 > Why?

Because that binding is in `global-map', which is shadowed by the
binding in `global-tty-map', in 21.5.

Use

(define-key global-tty-map [(control z)] 'suspend-emacs-or-iconify-frame)

I don't know the rationale for this change, but sometimes it's useful
to have different bindings depending on console type.  Personally I
think the shadowing keymap approach is preferable to rewriting the
global function to check whether it was invoked from a TTY or not.

It's possible that it would make sense to have global-set-key work on
global-tty-map as well as global-map, but that looks like a delicate
question at first glance.