bug#2873: Keybinding info for remapped commands could be more useful

[Drew Adams]

> >> When using a command, Emacs conveniently flashes the keybinding.
> >> For remapped commands, the message is not as useful:
> >> You can run the command `command' with <remap> <original-command>
> >> 
> >> It would probably be better to offer the binding of 
> >> original-command instead.
> 
> > Sounds related to bug #788, which mentioned the same 
> > problem for key mentions in menu items.
> 
> Indeed.  Back then I suggested to move the fix into where-is-internal
> and this bug report seems to show that it would indeed be a good idea.

Yidong recently made a temporary fix of #788: removing the key mention from such
menu items. If and when the bug gets fixed properly, we need to remember to
revert that temporary fix, so such keys will appear again (but properly) in menu
items. 

Dunno how you note such things so they aren't forgotten later - perhaps a
comment in the code?