docs: remove obsolete references to Autoconf 2.13

Autoconf 2.13 is definitely obsolete today, so giving hints or caveats
about it in the Automake documentation is not only obsolescent, but
also counter-productive, as it suggests that autoconf 2.13 is still
relevant.

* doc/automake.texi: Adjust.  Related rewordings.  Since we are at it,
prefer using a more modern autoconf version number (2.68 instead of 2.57)
in an example showing how to correctly use 'AC_PREREQ' in third-party
.m4 files.

Signed-off-by: Stefano Lattarini <stefano.lattarini@gmail.com>

diff --git a/doc/automake.texi b/doc/automake.texi
index b30968451639aafb75259f039a3345d2a5e212bf..c21a5b7e039a8db4dbbb8f85bbc8d1b27f618819 100644 (file)
--- a/doc/automake.texi
+++ b/doc/automake.texi
@@ -430,11 +430,7 @@ should generally be one @file{Makefile.am} per directory of a project.
 Automake does constrain a project in certain ways; for instance, it
 assumes that the project uses Autoconf (@pxref{Top, , Introduction,
 autoconf, The Autoconf Manual}), and enforces certain restrictions on
-the @file{configure.ac} contents@footnote{Older Autoconf versions used
-@file{configure.in}.  Autoconf 2.50 and greater promotes
-@file{configure.ac} over @file{configure.in}.  The rest of this
-documentation will refer to @file{configure.ac}, but Automake also
-supports @file{configure.in} for backward compatibility.}.
+the @file{configure.ac} contents.
 
 @cindex Automake requirements
 @cindex Requirements, Automake
@@ -3032,8 +3028,7 @@ This is required if any Objective C source is included.  @xref{Particular
 Programs, , Particular Program Checks, autoconf, The Autoconf Manual}.
 
 @item AC_PROG_F77
-This is required if any Fortran 77 source is included.  This macro is
-distributed with Autoconf version 2.13 and later.  @xref{Particular
+This is required if any Fortran 77 source is included.  @xref{Particular
 Programs, , Particular Program Checks, autoconf, The Autoconf Manual}.
 
 @item AC_F77_LIBRARY_LDFLAGS
@@ -3569,7 +3564,7 @@ For instance,
 
 @example
 # bad style
-AC_PREREQ(2.57)
+AC_PREREQ(2.68)
 AC_DEFUN(AX_FOOBAR,
 [AC_REQUIRE([AX_SOMETHING])dnl
 AX_FOO
@@ -3582,7 +3577,7 @@ should be rewritten as
 
 @example
 AC_DEFUN([AX_FOOBAR],
-[AC_PREREQ([2.57])dnl
+[AC_PREREQ([2.68])dnl
 AC_REQUIRE([AX_SOMETHING])dnl
 AX_FOO
 AX_BAR
@@ -3590,11 +3585,11 @@ AX_BAR
 @end example
 
 Wrapping the @code{AC_PREREQ} call inside the macro ensures that
-Autoconf 2.57 will not be required if @code{AX_FOOBAR} is not actually
+Autoconf 2.68 will not be required if @code{AX_FOOBAR} is not actually
 used.  Most importantly, quoting the first argument of @code{AC_DEFUN}
 allows the macro to be redefined or included twice (otherwise this
 first argument would be expanded during the second definition).  For
-consistency we like to quote even arguments such as @code{2.57} that
+consistency we like to quote even arguments such as @code{2.68} that
 do not require it.
 
 If you have been directed here by the @command{aclocal} diagnostic but
@@ -6594,10 +6589,9 @@ in the appropriate Fortran 77 intrinsic and run-time libraries.
 @cindex @code{FLIBS}, defined
 @vindex FLIBS
 These extra Fortran 77 linker flags are supplied in the output variable
-@code{FLIBS} by the @code{AC_F77_LIBRARY_LDFLAGS} Autoconf macro
-supplied with newer versions of Autoconf (Autoconf version 2.13 and
-later).  @xref{Fortran Compiler, , Fortran Compiler Characteristics,
-autoconf, The Autoconf Manual}.
+@code{FLIBS} by the @code{AC_F77_LIBRARY_LDFLAGS} Autoconf macro.
+@xref{Fortran Compiler, , Fortran Compiler Characteristics, autoconf,
+The Autoconf Manual}.
 @end enumerate
 
 If Automake detects that a program or shared library (as mentioned in
@@ -6959,20 +6953,14 @@ substitutions.  This means that if you are conditionally building a
 program using such a substitution, then your @file{configure.ac} must
 take care to add @samp{$(EXEEXT)} when constructing the output variable.
 
-With Autoconf 2.13 and earlier, you must explicitly use @code{AC_EXEEXT}
-to get this support.  With Autoconf 2.50, @code{AC_EXEEXT} is run
-automatically if you configure a compiler (say, through
-@code{AC_PROG_CC}).
-
 Sometimes maintainers like to write an explicit link rule for their
 program.  Without executable extension support, this is easy---you
 simply write a rule whose target is the name of the program.  However,
 when executable extension support is enabled, you must instead add the
 @samp{$(EXEEXT)} suffix.
 
-Unfortunately, due to the change in Autoconf 2.50, this means you must
-always add this extension.  However, this is a problem for maintainers
-who know their package will never run on a platform that has
+This might be a nuisance for maintainers who know their package will
+never run on a platform that has
 executable extensions.  For those maintainers, the @option{no-exeext}
 option (@pxref{Options}) will disable this feature.  This works in a
 fairly ugly way; if @option{no-exeext} is seen, then the presence of a