branch-1_4 depends on autoconf 2.60

[Eric Blake]

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Now that Ralf got the first release of autoconf out in a couple of years,
we can finally use its new features.  This 3-line change resulted in an
8k reduction to configure between two runs of autoconf 2.60.

2006-06-24  Eric Blake  <address@hidden>

        * configure.ac (AC_PREREQ): Autoconf 2.60 is now released.
        (AC_CHECK_HEADERS_ONCE): Use this new feature.
        (AC_CHECK_FUNCS_ONCE): Likewise.

- --
Life is short - so eat dessert first!

Eric Blake             address@hidden
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Index: configure.ac
===================================================================
RCS file: /sources/m4/m4/configure.ac,v
retrieving revision 1.36.2.16
diff -u -p -r1.36.2.16 configure.ac
--- configure.ac        22 Jun 2006 14:55:48 -0000      1.36.2.16
+++ configure.ac        24 Jun 2006 22:46:25 -0000
@@ -17,7 +17,7 @@
 # Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 # 02110-1301  USA
 
-AC_PREREQ([2.59])
+AC_PREREQ([2.60])
 AC_INIT([GNU M4], [1.4.4c], address@hidden)
 AM_INIT_AUTOMAKE([1.9.6 dist-bzip2 gnu])
 PACKAGE=$PACKAGE_TARNAME; AC_SUBST([PACKAGE])
@@ -32,7 +32,7 @@ AC_CONFIG_HEADERS([config.h:config-h.in]
 AC_PROG_CC
 M4_EARLY
 
-AC_CHECK_HEADERS([limits.h siginfo.h])
+AC_CHECK_HEADERS_ONCE([limits.h siginfo.h])
 AC_CHECK_TYPES([siginfo_t], [], [],
 [[#include <signal.h>
 #if HAVE_SIGINFO_H
@@ -46,7 +46,7 @@ AC_CHECK_MEMBERS([struct sigaction.sa_si
 AC_TYPE_SIGNAL
 AC_TYPE_SIZE_T
 
-AC_CHECK_FUNCS([sigaction sigaltstack sigstack sigvec strerror tmpfile])
+AC_CHECK_FUNCS_ONCE([sigaction sigaltstack sigstack sigvec strerror tmpfile])
 
 M4_INIT