autoconf: trunk post-release administrivia

https://github.com/libsdl-org/autoconf/commit/6d38e9fa2b39b3c3a8e4d6d7da38c59909d3f39d

From 6d38e9fa2b39b3c3a8e4d6d7da38c59909d3f39d Mon Sep 17 00:00:00 2001
From: Zack Weinberg <[EMAIL REDACTED]>
Date: Thu, 28 Jan 2021 17:54:10 -0500
Subject: [PATCH] trunk post-release administrivia

Matching the commits on the release branch:

* NEWS: Bring over record of release notes.
* .prev-version: Record previous version.
* cfg.mk (old_NEWS_hash): Auto-update.
---
 .prev-version |  2 +-
 NEWS          | 18 ++++++++++++++++++
 cfg.mk        |  2 +-
 3 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/.prev-version b/.prev-version
index 587cb39c..b93b4f20 100644
--- a/.prev-version
+++ b/.prev-version
@@ -1 +1 @@
-2.70
+2.71
diff --git a/NEWS b/NEWS
index e6f5d8c3..8b4f9d64 100644
--- a/NEWS
+++ b/NEWS
@@ -7,6 +7,24 @@ GNU Autoconf NEWS - User visible changes.
 ** Obsolete features and new warnings
 ** Notable bug fixes
 
+* Noteworthy changes in release 2.71 (2021-01-28) [stable]
+
+** Bug fixes, including:
+
+*** Compilers that support C99 but not C2011 are detected correctly.
+
+*** Compatibility improved with clang and Oracle C++.
+
+*** Compatibility restored with automake's rules for regenerating configure.
+
+*** Compatibility restored with old versions of std-gnu11.m4.
+
+  Packages that wish to maintain compatibility with Autoconf 2.69 or
+  older, should update their copy of std-gnu11.m4 from Gnulib as soon
+  as practical, as the compatibility code bulks up the configure script.
+
+  Packages that require Autoconf 2.70 can drop this file entirely.
+
 * Noteworthy changes in release 2.70 (2020-12-08) [stable]
 
 ** Backward incompatibilities:
diff --git a/cfg.mk b/cfg.mk
index ce6edfdb..0d4ec728 100644
--- a/cfg.mk
+++ b/cfg.mk
@@ -84,7 +84,7 @@ update-release-year:
 .PHONY: update-release-year
 
 # Prevent incorrect NEWS edits.
-old_NEWS_hash = 152f03614545887231fddaf67821b4d4
+old_NEWS_hash = 981169afdd2c97642125938f80a26b7f
 
 exclude_file_name_regexp--sc_prohibit_undesirable_word_seq = \
   ^(maint\.mk|build-aux/texinfo\.tex)$$