bug#29420: 26.0; doc of `list-packages'

[Drew Adams]

`C-h f list-packages' should give you a better description of the
display that results.  It wouldn't hurt to succinctly describe each
column.

`C-h r g package menu' should give you a better description.  It should
describe each column of the display.  It could describe column `status'
better, for instance.  Apparently one of the possible values is
`dependency', but that is not mentioned.

Cf. https://emacs.stackexchange.com/q/37058/105



In GNU Emacs 26.0.90 (build 3, x86_64-w64-mingw32)
 of 2017-10-13
Repository revision: 906224eba147bdfc0514090064e8e8f53160f1d4
Windowing system distributor `Microsoft Corp.', version 6.1.7601
Configured using:
 `configure --without-dbus --host=x86_64-w64-mingw32
 --without-compress-install 'CFLAGS=-O2 -static -g3''