year2038-recommended: new module

Remove year2038-required and largefile-required, replacing
the former with year2038-recommended and simply removing
the latter.  This syncs with Autoconf master.
* MODULES.html.sh, NEWS, doc/largefile.texi:
* all-modules (exclude): Exclude year2038-recommended, not -required.
* doc/posix-headers/sys_types.texi, doc/posix-headers/time.texi:
* doc/year2038.texi: Mention this.
* m4/largefile.m4: Sync from Autoconf.  Override existing macros
if AC_SYS_YEAR2038_RECOMMENDED is not defined, rather than if
AC_SYS_LARGEFILE_REQUIRED is not defined.
* modules/largefile-required, modules/year2038-required: Removed.
* modules/year2038: Do not depend on largefile; simply
use m4/largefile.m4, since we shouldn’t need the extra goodies
largefile supplies.
* modules/year2038-recommended: New module.

4 files changed, 29 insertions, 28 deletions

diff --git a/doc/largefile.texi b/doc/largefile.texi
index b5bfa5116a..574753f10a 100644
--- a/doc/largefile.texi
+++ b/doc/largefile.texi
@@ -1,22 +1,25 @@
 @node Large File Support
 @section Large File Support
 
-The Gnulib @samp{largefile-required} module provides support for files
-2 GiB and larger, or with device or inode numbers exceeding 32 bits.
-To this effect, it ensures that types like @code{off_t} and
+This module provides support for files 2 GiB and larger, or with
+device or inode numbers exceeding 32 bits.
+To this effect, it attempts to ensure that types like @code{off_t} and
 @code{ino_t} are 64-bit,
 at least on the following platforms:
 glibc, Mac OS X, FreeBSD, NetBSD, OpenBSD, AIX, HP-UX, IRIX, Solaris,
 Cygwin, mingw, MSVC.
 
-The Gnulib @samp{largefile} module is similar, except that it gives
+If the types cannot be made 64-bit, @command{configure} issues a
+warning and proceeds.
+
+This module gives
 @command{configure} an option @samp{--disable-largefile} that
 suppresses support for large files.  This may be useful if the package
 links to other libraries whose user-facing ABIs still require
 @code{off_t} or most other file-related types to be 32-bit on your
 platform.
 
-Both modules also add to @command{configure} an option
+This module also adds to @command{configure} an option
 @code{--enable-year2038}, needed on some platforms to access files
 with timestamps past the year 2038.  @xref{Avoiding the year 2038
 problem}.
diff --git a/doc/posix-headers/sys_types.texi b/doc/posix-headers/sys_types.texi
index 7590e78695..8739cc2625 100644
--- a/doc/posix-headers/sys_types.texi
+++ b/doc/posix-headers/sys_types.texi
@@ -38,7 +38,6 @@ are signed integer types that are wider than @code{long}:
 glibc x32
 @end itemize
 
-This module, together with the modules @code{largefile-required}
-or @code{largefile}, also defines the type
+This module, together with the module @code{largefile}, also defines the type
 @code{off_t} to a 64-bit integer type on some platforms:
 mingw, MSVC 14.
diff --git a/doc/posix-headers/time.texi b/doc/posix-headers/time.texi
index 70814d6cda..c1e22b9369 100644
--- a/doc/posix-headers/time.texi
+++ b/doc/posix-headers/time.texi
@@ -18,8 +18,7 @@ expressions:
 NetBSD 5.0.
 @end itemize
 
-Portability problems fixed by the Gnulib module
-@code{year2038} or @code{year2038-required}:
+Portability problems fixed by the Gnulib module @code{year2038}:
 @itemize
 @item
 On some platforms where @code{time_t} defaults to 32-bit but can be
diff --git a/doc/year2038.texi b/doc/year2038.texi
index f0f6d51516..5964601831 100644
--- a/doc/year2038.texi
+++ b/doc/year2038.texi
@@ -1,7 +1,7 @@
 @node Avoiding the year 2038 problem
 @section Avoiding the year 2038 problem
 
-The ``year 2038 problem'' denotes unpredictable behaviour that will
+The @dfn{year 2038 problem} denotes unpredictable behaviour that will
 likely occur in the year 2038, for programs that use a 32-bit signed
 integer @samp{time_t} type that cannot represent timestamps on or
 after 2038-01-19 03:14:08 UTC@.  See
@@ -26,32 +26,32 @@ suppresses support for post-2038 timestamps.  This may be useful if
 the package links to other libraries whose user-facing ABIs still
 require @code{time_t} to be 32-bit on your platform.
 
-The Gnulib module @samp{year2038-required} is like @samp{year2038},
-except it rejects platforms where @code{time_t} cannot represent
-timestamps after 2038, and it lacks a @option{--disable-year2038}
-option.  If this module is used and a 32-platform cannot support
+The Gnulib module @samp{year2038-recommended} is like @samp{year2038},
+except it by default rejects platforms where @code{time_t} cannot represent
+timestamps after 2038.  If this module is used and a 32-platform cannot support
 64-bit @code{time_t}, one can still fix the year-2038 problem by using
 a 64-bit instead of a 32-bit build, as noted in the architecture list
 below.  If all else fails one can configure with
-@samp{ac_year2038_required=no}; however, the resulting programs will
+@option{--disable-year2038}; however, the resulting programs will
 mishandle timestamps after 2038.
 
-The Gnulib module @samp{year2038-required} is
-recommended for packages intended for use on 32-bit platforms
-after the year 2038.  However, if your package needs to support
+The Gnulib module @samp{year2038-recommended} is designed
+for packages intended for use on 32-bit platforms
+after the year 2038.  If your package is commonly built on
 32-bit platforms that will not be used after the year 2038,
-you can use the @samp{year2038} module instead.
+you can use the @samp{year2038} module instead, to save builders
+the trouble of configuring with @option{--disable-year2038}.
 
 If the Gnulib module @samp{largefile} is used but neither
-@samp{year2038} nor @samp{year2038-required} is used,
+@samp{year2038} nor @samp{year2038-recommended} is used,
 @command{configure} will have an option @option{--enable-year2038}
 that causes @code{configure} to behave as if @samp{year2038} was used.
 This is for packages that have long used @samp{largefile} but have not
 gotten around to upgrading their Gnulib module list to include
-@samp{year2038} or @samp{year2038-required}.
+@samp{year2038} or @samp{year2038-recommended}.
 @xref{Large File Support}.
 
-With the @samp{year2038-required} module, @command{configure} by
+With the @samp{year2038-recommended} module, @command{configure} by
 default should work on the following 32-bit platforms (or 32-bit ABIs
 in bi-arch systems):
 
@@ -70,18 +70,18 @@ OpenBSD 5.5 (2014) and later on x86,
 @item
 FreeBSD/arm,
 @item
-Minix 3.3.
+Minix 3.3 (2014).
 @end itemize
 
 @noindent
-Whereas @command{configure} with @samp{year2038-required} will fail on
-earlier versions of the abovementioned platforms if a version is listed,
-and it will also fail on all versions of the following older 32-bit
-platforms or ABIs:
+Whereas with @samp{year2038-recommended}, @command{configure} should
+by default fail on earlier versions of the abovementioned platforms if
+a version is listed, and it should also by default fail on all
+versions of the following older 32-bit platforms or ABIs:
 
 @itemize
 @item
-Android,
+Android on ARMv7 or x86,
 @item
 Mac OS X 10.6 (2009) and earlier on x86 and powerpc,
 @item