[libgpiod][PATCH] build: drop obsolete autoconf macro

[Bartosz Golaszewski <brgl@xxxxxxxx>]

From: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx>

AC_HEADER_STDC is deprecated and should be replaced with
AC_CHECK_INCLUDES_DEFAULT. We haven't done this until now because the
latter is only available since autoconf v2.71. We kept supporting v2.69
for the sake of Debian stable but it has since upgraded to autoconf v2.71
so we update configure.ac as well and fix an autoconf warning.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx>
---
 configure.ac | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/configure.ac b/configure.ac
index cfa0997..b12db22 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1,7 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0-or-later
 # SPDX-FileCopyrightText: 2017-2022 Bartosz Golaszewski <brgl@xxxxxxxx>
 
-AC_PREREQ([2.69])
+AC_PREREQ([2.71])
 
 AC_INIT([libgpiod], [2.2])
 AC_SUBST(EXTRA_VERSION, [-rc2])
@@ -74,7 +74,8 @@ AC_DEFUN([HEADER_NOT_FOUND_CXX],
 	[ERR_NOT_FOUND([$1 header], [C++ bindings])])
 
 # This is always checked (library needs this)
-AC_HEADER_STDC
+AC_CHECK_INCLUDES_DEFAULT
+
 AC_FUNC_MALLOC
 AC_HEADER_STDBOOL
 AC_CHECK_FUNC([ioctl], [], [FUNC_NOT_FOUND_LIB([ioctl])])
-- 
2.43.0