bug#38457: 27.0.50; dabbrev-expand regression due to message change

[Stephen Berman]

0. emacs -Q
1. M-! te M-/

=> It takes about 4 seconds on my machine for the expansion "text" to
appear, during which the minibuffer displays "[Scanning for
dabbrevs...100%]" and then "[Scanning for dabbrevs...done]".  On builds
without this regression, the expansion is virtually instantaneous and no
message is seen in the minibuffer.

Git bisect pinpoints the following change:

aa89c84e00d8dc85100e6fedab7631c415e6364d is the first bad commit
commit aa89c84e00d8dc85100e6fedab7631c415e6364d
Author: Juri Linkov <juri@linkov.net>
Date:   Wed Nov 27 01:43:49 2019 +0200

    message uses minibuffer-message in the active minibuffer (bug#17272 
bug#19064)

    * doc/lispref/display.texi (Displaying Messages): Explain the
    behavior of using minibuffer-message if the minibuffer is active.

    * src/editfns.c (Fmessage_in_echo_area): New function with body
    copied from Fmessage.
    (Fmessage): Call minibuffer-message in the active minibuffer,
    otherwise call Fmessage_in_echo_area.
    (message-in-echo-area): New variable.

    * lisp/isearch.el (isearch--momentary-message, isearch-message):
    * lisp/minibuffer.el (minibuffer-message, minibuffer-completion-help):
    Use 'message-in-echo-area' instead of 'message' where necessary.

    * lisp/autorevert.el (auto-revert-handler):
    * lisp/man.el (Man-bgproc-sentinel):
    * lisp/subr.el (do-after-load-evaluation):
    Revert recent changes that replaced 'message' with 'minibuffer-message'.
    This is not needed anymore since 'message' uses 'minibuffer-message'
    in the active minibuffer.


In GNU Emacs 27.0.50 (build 27, x86_64-pc-linux-gnu, GTK+ Version 3.24.5, cairo 
version 1.16.0)
 of 2019-12-01 built on strobe-lfs84
Repository revision: 9f2145f42daab13aed5cf89fdb6a7c5579819ec0
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12003000
System Description: Linux From Scratch

Configured using:
 'configure --with-cairo 'CFLAGS=-Og -g3'
 PKG_CONFIG_PATH=/opt/qt5/lib/pkgconfig'

Configured features:
XPM JPEG TIFF GIF PNG RSVG CAIRO SOUND DBUS GSETTINGS GLIB NOTIFY
INOTIFY ACL GNUTLS LIBXML2 FREETYPE HARFBUZZ M17N_FLT LIBOTF ZLIB
TOOLKIT_SCROLL_BARS GTK3 X11 XDBE XIM MODULES THREADS JSON PDUMPER LCMS2
GMP