bug#22334: 25.1.50; Better sorting of blocks in describe-bindings

[Eli Zaretskii <eliz@gnu.org>]

> From: Eric Abrahamsen <eric@ericabrahamsen.net>
> Date: Sat, 09 Jan 2016 11:31:03 +0800
> 
> When using `describe-bindings' to see the current key bindings in
> effect, I'd like the major mode bindings to be sorted to the top of the
> buffer, followed by the minor modes.

That's what I see we do now: the major mode is first, followed by the
minor modes.  There's a part with links to minor modes, in case the
user knows which minor mode she wants to read about.

> Right now the sorting of blocks seems random, though every time the
> top block is twenty screens or so of self-inserting bindings (or
> maybe it's compose sequences?) which are never what I want to see,
> and are a pain to scroll past.

Please show an example of that, because this is definitely specific to
the major mode.  E.g., I don't see this for *scratch*.

> While we're at it, minor modes with no bindings in effect could just
> as well be omitted.

It only takes a line or two; omitting that would be losing
information, IMO.