Use autoconf 2.71

Signed-off-by: Alexey Gladkov <[email protected]>

INSTALL

@@ -1,8 +1,8 @@
 Installation Instructions
 *************************
 
-   Copyright (C) 1994-1996, 1999-2002, 2004-2016 Free Software
-Foundation, Inc.
+   Copyright (C) 1994-1996, 1999-2002, 2004-2017, 2020-2021 Free
+Software Foundation, Inc.
 
    Copying and distribution of this file, with or without modification,
 are permitted in any medium without royalty provided the copyright
@@ -225,7 +225,7 @@ order to use an ANSI C compiler:
 
 and if that doesn't work, install pre-built binaries of GCC for HP-UX.
 
-   HP-UX 'make' updates targets which have the same time stamps as their
+   HP-UX 'make' updates targets which have the same timestamps as their
 prerequisites, which makes it generally unusable when shipped generated
 files such as 'configure' are involved.  Use GNU 'make' instead.
 

configure.ac

@@ -2,7 +2,7 @@
 # Process this file with autoconf to produce a configure script.
 AC_INIT([kbd],[2.6.2],[[email protected]],[],[https://kbd-project.org/])
 
-AC_PREREQ([2.69])
+AC_PREREQ([2.71])
 
 AC_CONFIG_AUX_DIR(config)
 AC_CONFIG_MACRO_DIR([m4])
@@ -21,10 +21,9 @@ AM_SILENT_RULES([yes])
 CFLAGS="${CFLAGS:-}"
 
 AC_PROG_CC
-AC_PROG_CC_C99
 AM_PROG_CC_C_O
 AC_PROG_YACC
-AC_PROG_LEX
+AC_PROG_LEX([noyywrap])
 AC_PROG_SED
 AC_PROG_INSTALL
 AC_PROG_LN_S
@@ -41,7 +40,6 @@ ALL_LINGUAS=`cd $srcdir/po > /dev/null && echo *.po | sed 's/\.po//g'`
 
 # Checks for header files.
 AC_HEADER_DIRENT
-AC_HEADER_STDC
 AC_HEADER_SYS_WAIT
 AC_CHECK_HEADERS([fcntl.h libintl.h locale.h memory.h stdlib.h string.h \
 sys/file.h sys/ioctl.h termios.h unistd.h])