Install gnulib to make sure we can use argp in ltlfilt.

* lib/Makefile.am, lib/alloca.c, lib/alloca.in.h, lib/argp-ba.c,
lib/argp-eexst.c, lib/argp-fmtstream.c, lib/argp-fmtstream.h,
lib/argp-fs-xinl.c, lib/argp-help.c, lib/argp-namefrob.h,
lib/argp-parse.c, lib/argp-pin.c, lib/argp-pv.c, lib/argp-pvh.c,
lib/argp-xinl.c, lib/argp.h, lib/asnprintf.c, lib/basename-lgpl.c,
lib/dirname-lgpl.c, lib/dirname.h, lib/dosname.h, lib/errno.in.h,
lib/float+.h, lib/float.c, lib/float.in.h, lib/getopt.c,
lib/getopt.in.h, lib/getopt1.c, lib/getopt_int.h, lib/gettext.h,
lib/intprops.h, lib/itold.c, lib/malloc.c, lib/memchr.c,
lib/memchr.valgrind, lib/mempcpy.c, lib/printf-args.c,
lib/printf-args.h, lib/printf-parse.c, lib/printf-parse.h,
lib/rawmemchr.c, lib/rawmemchr.valgrind, lib/size_max.h,
lib/sleep.c, lib/stdalign.in.h, lib/stdbool.in.h, lib/stddef.in.h,
lib/stdint.in.h, lib/stdio.in.h, lib/stdlib.in.h, lib/strcasecmp.c,
lib/strchrnul.c, lib/strchrnul.valgrind, lib/strerror-override.c,
lib/strerror-override.h, lib/strerror.c, lib/string.in.h,
lib/strings.in.h, lib/stripslash.c, lib/strncasecmp.c,
lib/strndup.c, lib/strnlen.c, lib/sys_types.in.h, lib/sysexits.in.h,
lib/unistd.in.h, lib/vasnprintf.c, lib/vasnprintf.h, lib/verify.h,
lib/vsnprintf.c, lib/wchar.in.h, lib/xsize.h, m4/00gnulib.m4,
m4/alloca.m4, m4/argp.m4, m4/dirname.m4, m4/double-slash-root.m4,
m4/errno_h.m4, m4/exponentd.m4, m4/extensions.m4, m4/float_h.m4,
m4/getopt.m4, m4/gnulib-cache.m4, m4/gnulib-common.m4,
m4/gnulib-comp.m4, m4/gnulib-tool.m4, m4/include_next.m4,
m4/intmax_t.m4, m4/inttypes_h.m4, m4/longlong.m4, m4/malloc.m4,
m4/math_h.m4, m4/memchr.m4, m4/mempcpy.m4, m4/mmap-anon.m4,
m4/multiarch.m4, m4/nocrash.m4, m4/off_t.m4, m4/printf.m4,
m4/rawmemchr.m4, m4/size_max.m4, m4/sleep.m4, m4/ssize_t.m4,
m4/stdalign.m4, m4/stdbool.m4, m4/stddef_h.m4, m4/stdint.m4,
m4/stdint_h.m4, m4/stdio_h.m4, m4/stdlib_h.m4, m4/strcase.m4,
m4/strchrnul.m4, m4/strerror.m4, m4/string_h.m4, m4/strings_h.m4,
m4/strndup.m4, m4/strnlen.m4, m4/sys_socket_h.m4, m4/sys_types_h.m4,
m4/sysexits.m4, m4/unistd_h.m4, m4/vasnprintf.m4, m4/vsnprintf.m4,
m4/warn-on-use.m4, m4/wchar_h.m4, m4/wchar_t.m4, m4/wint_t.m4,
m4/xsize.m4, tools/snippet/_Noreturn.h, tools/snippet/arg-nonnull.h,
tools/snippet/c++defs.h, tools/snippet/warn-on-use.h: New files from
gnulib 1af55d85d9762a679b4302d5995f05ccd883e956.
* configure.ac, Makefile.am: Adjust to compile gnulib.
* src/bin/Makefile.am: Adjust to use gnulib.
* README: Mention lib/.

m4/strchrnul.m4

@@ -0,0 +1,50 @@
+# strchrnul.m4 serial 9
+dnl Copyright (C) 2003, 2007, 2009-2012 Free Software Foundation, Inc.
+dnl This file is free software; the Free Software Foundation
+dnl gives unlimited permission to copy and/or distribute it,
+dnl with or without modifications, as long as this notice is preserved.
+
+AC_DEFUN([gl_FUNC_STRCHRNUL],
+[
+  dnl Persuade glibc <string.h> to declare strchrnul().
+  AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS])
+
+  AC_REQUIRE([gl_HEADER_STRING_H_DEFAULTS])
+  AC_CHECK_FUNCS([strchrnul])
+  if test $ac_cv_func_strchrnul = no; then
+    HAVE_STRCHRNUL=0
+  else
+    AC_CACHE_CHECK([whether strchrnul works],
+      [gl_cv_func_strchrnul_works],
+      [AC_RUN_IFELSE([AC_LANG_PROGRAM([[
+#include <string.h> /* for strchrnul */
+]], [[const char *buf = "a";
+      return strchrnul (buf, 'b') != buf + 1;
+    ]])],
+        [gl_cv_func_strchrnul_works=yes],
+        [gl_cv_func_strchrnul_works=no],
+        [dnl Cygwin 1.7.9 introduced strchrnul, but it was broken until 1.7.10
+         AC_EGREP_CPP([Lucky user],
+           [
+#if defined __CYGWIN__
+ #include <cygwin/version.h>
+ #if CYGWIN_VERSION_DLL_COMBINED > CYGWIN_VERSION_DLL_MAKE_COMBINED (1007, 9)
+  Lucky user
+ #endif
+#else
+  Lucky user
+#endif
+           ],
+           [gl_cv_func_strchrnul_works="guessing yes"],
+           [gl_cv_func_strchrnul_works="guessing no"])
+        ])
+      ])
+    case "$gl_cv_func_strchrnul_works" in
+      *yes) ;;
+      *) REPLACE_STRCHRNUL=1 ;;
+    esac
+  fi
+])
+
+# Prerequisites of lib/strchrnul.c.
+AC_DEFUN([gl_PREREQ_STRCHRNUL], [:])