bug#24880: 26.0.50; buff-menu: Command to unmark all buffers

[Eli Zaretskii]

> From: Tino Calancha <tino.calancha@gmail.com>
> Date: Sat, 05 Nov 2016 19:04:15 +0900
> 
> I miss in this package a command to unmark all buffers bound to 'U'.
> How about the following?

No objections from me, but please add suitable changes to NEWS and the
user manual.

Also, wrt this:

> * lisp/buff-menu.el (Buffer-menu-unmark-all):
> New command; cancel all requested operations on buffers.
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
I'd suggest to say "remove all flags from all the lines" instead, as
it describes better what is being done.

Thanks.