bug#60470: 26.3; Doc string of `recentf-keep'

[Drew Adams]

Please consider saying in the doc string what it means to "keep" a file
name in the recent list.

The doc string goes into what it means to be a predicate, but it says
nothing, really, about what this option means/does, because it tells you
nothing about what "keeping" amounts to.

Also, a nit: when used as a noun phrase, "filename" should be "file
name".  (When used as an adjective before a noun phrase it should be
"file-name".  We use (should use) "filename" only in some function
etc. names, not in the doc.


In GNU Emacs 26.3 (build 1, x86_64-w64-mingw32)
 of 2019-08-29
Repository revision: 96dd0196c28bc36779584e47fffcca433c9309cd
Windowing system distributor `Microsoft Corp.', version 10.0.19044
Configured using:
 `configure --without-dbus --host=x86_64-w64-mingw32
 --without-compress-install 'CFLAGS=-O2 -static -g3''