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diff --git a/gnulib-m4/sleep.m4 b/gnulib-m4/sleep.m4
new file mode 100644
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+++ b/gnulib-m4/sleep.m4
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+# sleep.m4 serial 8
+dnl Copyright (C) 2007-2017 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_SLEEP],
+[
+  AC_REQUIRE([gl_UNISTD_H_DEFAULTS])
+  AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
+  dnl We expect to see the declaration of sleep() in a header file.
+  dnl Older versions of mingw have a sleep() function that is an alias to
+  dnl _sleep() in MSVCRT. It has a different signature than POSIX sleep():
+  dnl it takes the number of milliseconds as argument and returns void.
+  dnl mingw does not declare this function.
+  AC_CHECK_DECLS([sleep], , , [[#include <unistd.h>]])
+  AC_CHECK_FUNCS_ONCE([sleep])
+  if test $ac_cv_have_decl_sleep != yes; then
+    HAVE_SLEEP=0
+  else
+    dnl Cygwin 1.5.x has a bug where sleep can't exceed 49.7 days.
+    AC_CACHE_CHECK([for working sleep], [gl_cv_func_sleep_works],
+      [AC_RUN_IFELSE([AC_LANG_PROGRAM([[
+#include <errno.h>
+#include <unistd.h>
+#include <signal.h>
+static void
+handle_alarm (int sig)
+{
+  if (sig != SIGALRM)
+    _exit (2);
+}
+]], [[
+    /* Failure to compile this test due to missing alarm is okay,
+       since all such platforms (mingw) also lack sleep.  */
+    unsigned int pentecost = 50 * 24 * 60 * 60; /* 50 days.  */
+    unsigned int remaining;
+    signal (SIGALRM, handle_alarm);
+    alarm (1);
+    remaining = sleep (pentecost);
+    if (remaining > pentecost)
+      return 3;
+    if (remaining <= pentecost - 10)
+      return 4;
+    return 0;
+    ]])],
+      [gl_cv_func_sleep_works=yes], [gl_cv_func_sleep_works=no],
+      [case "$host_os" in
+                 # Guess yes on glibc systems.
+         *-gnu*) gl_cv_func_sleep_works="guessing yes" ;;
+                 # Guess no on native Windows.
+         mingw*) gl_cv_func_sleep_works="guessing no" ;;
+                 # If we don't know, assume the worst.
+         *)      gl_cv_func_sleep_works="guessing no" ;;
+       esac
+      ])])
+    case "$gl_cv_func_sleep_works" in
+      *yes) ;;
+      *)
+        REPLACE_SLEEP=1
+        ;;
+    esac
+  fi
+])