bug#37447: 26.3; Commands on <delete> and <backspace>

[Sebastian Urban]

> These key bindings are too old to change them in the default
> configuration.

So inconsistency with 'M-d' and 'M-<delete>' will stay and
'C-<backspace>' & 'M-<backspace>' doing the same thing will also stay
because of history?  I could ignore 'C-S-<backspace>', but previous
two cases should be "updated".

But if "No." means "No." - close the bug, please.  Unless we are
waiting for more opinions.