[PATCH app-sessreg] Add AC_USE_SYSTEM_EXTENSIONS providing needed WTMPX_FILE define

[Gaetan Nadon]

The WTMPX_FILE is only defined under __USE_GNU conditional
compilation. Autoconf provides AC_USE_SYSTEM_EXTENSIONS
to enable platform extensions.

It must be expanded before any other macros that uses the compiler.
To reduce the risk of being misplaced, the statements have been
grouped (mostly) as per the GNU standard layout.This macro
requires Autoconf level 2.60 or later.

The compilation failed under a GNU-Linux OS.

Tested-by (on darwin): Jeremy Huddleston <jeremyhu at apple.com>
Signed-off-by: Gaetan Nadon <memsize at videotron.ca>
---
 configure.ac |   32 +++++++++++++++++++-------------
 1 files changed, 19 insertions(+), 13 deletions(-)

diff --git a/configure.ac b/configure.ac
index be1b4b4..6287a6b 100644
--- a/configure.ac
+++ b/configure.ac
@@ -20,25 +20,34 @@ dnl  PERFORMANCE OF THIS SOFTWARE.
 dnl
 dnl Process this file with autoconf to create configure.
 
-AC_PREREQ([2.57])
+# Initialize Autoconf
+AC_PREREQ([2.60])
 AC_INIT(sessreg, [1.0.5],
 	[https://bugs.freedesktop.org/enter_bug.cgi?product=xorg],
 	sessreg)
+AC_CONFIG_SRCDIR([Makefile.am])
+AC_CONFIG_HEADERS([config.h])
+AC_CANONICAL_HOST
+AC_GNU_SOURCE
+AC_SYS_LARGEFILE
+
+# Initialize Automake
 AM_INIT_AUTOMAKE([foreign dist-bzip2])
 AM_MAINTAINER_MODE
 
-AM_CONFIG_HEADER(config.h)
-
-# Require xorg-macros 1.3 or later: XORG_DEFAULT_OPTIONS
+# Require xorg-macros: XORG_DEFAULT_OPTIONS
 m4_ifndef([XORG_MACROS_VERSION],
-	  [m4_fatal([must install xorg-macros 1.3 or later before running autoconf/autogen])])
-XORG_MACROS_VERSION(1.3)
+	  [m4_fatal([must install xorg-macros 1.4 or later before running autoconf/autogen])])
+XORG_MACROS_VERSION(1.4)
+XORG_DEFAULT_OPTIONS
+XORG_WITH_LINT
 
+# Checks for programs.
 AC_PROG_CC
+AC_PROG_CC_C99
 AC_PROG_INSTALL
 
-XORG_DEFAULT_OPTIONS
-
+# Checks for header files.
 AC_CHECK_HEADERS([lastlog.h utmp.h utmpx.h sys/param.h])
 AC_CHECK_MEMBER([struct utmpx.ut_syslen],
 		HAVE_SYSLEN=1,
@@ -46,15 +55,12 @@ AC_CHECK_MEMBER([struct utmpx.ut_syslen],
 		[#include <utmpx.h>])
 AC_DEFINE_UNQUOTED(HAVE_UTMPX_UT_SYSLEN,$HAVE_SYSLEN,
 		   [utmpx structure includes ut_syslen field])
-AC_CHECK_FUNCS([updwtmpx utmpxname])
 
-AC_SYS_LARGEFILE
+# Checks for typedefs, structures, and compiler characteristics.
+AC_CHECK_FUNCS([updwtmpx utmpxname])
 
 # Checks for pkg-config packages
 PKG_CHECK_MODULES(SESSREG, xproto)
 AC_SUBST(SESSREG_CFLAGS)
 
-# Allow checking code with lint, sparse, etc.
-XORG_WITH_LINT
-
 AC_OUTPUT([Makefile])
-- 
1.6.0.4