Subject: Add gnus-summary-sort-by-subject-reversed

From: 積丹尼 Dan Jacobson <[email-masked]>
Date: Tue, 13 Mar 2018 10:21:54 +0800

Sure, (gnus-summary-sort-by-subject &optional REVERSE)
has REVERSE. But you also need a different kind of reverse, the "man
rev(1)" kind of reverse, to group subjects like these,
    1 180311180| -97.1|黃艾崴        :黃艾崴 sent a message to the conversation "3/10台中聚會."
    1 180311181| -98.6|方佳盈        :方佳盈 sent a message to the conversation "3/10台中聚會."
    1 180311180| -98.6|黃艾崴        :黃艾崴 sent a message to the conversation "3/10台中聚會."

Gnus v5.13
GNU Emacs 25.2.2 (x86_64-pc-linux-gnu, GTK+ Version 3.22.28)
 of 2018-02-19, modified by Debian