DEL vs Backspace (was: Proposal for an improved `help-for-help')

[Stefan Monnier]

> As you say, this is an old problem.  For example `C-h k <backspace>'
> here gives a help screen that cryptically says "DEL (translated from
> <backspace>)".  I suppose most users have no idea what that means, other
> than some vague notion that "DEL is clearly just the same as backspace".

This is harder to fix, but maybe we should tackle those problem.
Basically, the issue is that we have two different events: the symbol
`backspace` generated under GUIs and the DEL character (aka ^?)
generated under ttys.

The way we unify them is via `function-key-map` which maps `backspace`
to DEL when there's no binding for `backspace`.

Maybe we should inverse this mapping.  Similarly for RET-vs-return and
TAB-vs-tab.

Another benefit in the long run would be to free C-i and C-m for the
users to bind as they please in GUI frames.


        Stefan