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

[Sebastian Urban <mrsebastianurban@gmail.com>]

> Imagine many users using the same keys for years, and now
> they will start doing the opposite - a recipe for disaster.

And that's why I'm not proposing changing C-b/n/p/f to C-h/j/k/l.  But
these two cases (without C-S-<backspace>) I pointed out doesn't seem
very critical, moreover they look like a bug (with 'M-<delete>'
deleting backward instead of forward as 'M-d' does - 'C-d' does
similar thing do <delete>, so 'M-...' should also be similar) or like
a leftover from the past ('C-<backspace>') that could be reused for
something useful.

Also, there are "obsolete" functions that are removed after few
versions of Emacs, so why not do the same thing to key bindings?  They
don't change that often, so it won't be a revolution, right?  Keeping
old key bindings forever(?), especially when user can change them, is
rather strange - confusion among new users, less keys for new/other
commands, etc.  I think Emacs should have one default key per command,
older should be marked as "obsolete" and removed after 1 or 2 major
versions.

But, this is from perspective of a beginner, so...