[NetworkManager-vpnc/lr/gettext: 1/2] build: deal with some autoconf warnings

[Lubomir Rintel <lkundrak src gnome org>]

commit d66562786ff7b737419f8bfab209de7a9831bf16
Author: Lubomir Rintel <lkundrak v3 sk>
Date:   Mon Jun 27 16:21:01 2022 +0200

    build: deal with some autoconf warnings
    
    The remaining one is about GLIB_GNU_GETTEXT, we'll deal with that in a
    subsequent commit.

 configure.ac | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 7ba9f66..64929a8 100644
--- a/configure.ac
+++ b/configure.ac
@@ -11,16 +11,17 @@ AC_CONFIG_MACRO_DIR([m4])
 
 AC_CONFIG_HEADERS([config.h])
 
+AC_USE_SYSTEM_EXTENSIONS
+
 dnl
 dnl Require programs
 dnl
 AC_PROG_CC
 AM_PROG_CC_C_O
 AC_PROG_INSTALL
-AC_PROG_LIBTOOL
+LT_INIT
 AC_PATH_PROG(GLIB_COMPILE_RESOURCES, glib-compile-resources)
 
-AC_GNU_SOURCE
 
 AC_CHECK_PROG([has_file], file, yes, no)
 if test x$has_file = xno ; then
@@ -35,7 +36,6 @@ fi
 dnl
 dnl Required headers
 dnl
-AC_HEADER_STDC
 AC_CHECK_HEADERS(fcntl.h paths.h sys/ioctl.h sys/time.h syslog.h unistd.h)
 
 dnl
@@ -43,7 +43,6 @@ dnl Checks for typedefs, structures, and compiler characteristics.
 dnl
 AC_TYPE_MODE_T
 AC_TYPE_PID_T
-AC_HEADER_TIME
 
 dnl
 dnl Checks for library functions.