Update from Gnulib

This incorporates:
2020-08-13 sys_random: Work around an uClibc bug
* lib/sys_random.in.h, m4/getrandom.m4, m4/sys_random_h.m4:
Copy from Gnulib.

lib/sys_random.in.h

@@ -23,6 +23,10 @@
 
 #if @HAVE_SYS_RANDOM_H@
 
+/* On uClibc, <sys/random.h> assumes prior inclusion of <stddef.h>.  */
+# if defined __UCLIBC__
+#  include <stddef.h>
+# endif
 /* On Mac OS X 10.5, <sys/random.h> assumes prior inclusion of <sys/types.h>.
    On Max OS X 10.13, <sys/random.h> assumes prior inclusion of a file that
    includes <Availability.h>, such as <stdlib.h> or <unistd.h>.  */

m4/getrandom.m4

@@ -1,4 +1,4 @@
-# getrandom.m4 serial 7
+# getrandom.m4 serial 8
 dnl Copyright 2020 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -18,7 +18,8 @@ AC_DEFUN([gl_FUNC_GETRANDOM],
       [gl_cv_func_getrandom_ok],
       [AC_COMPILE_IFELSE(
          [AC_LANG_PROGRAM(
-            [[/* Additional includes are needed before <sys/random.h> on Mac OS X.  */
+            [[/* Additional includes are needed before <sys/random.h> on uClibc
+                 and Mac OS X.  */
               #include <sys/types.h>
               #include <stdlib.h>
               #include <sys/random.h>

m4/sys_random_h.m4

@@ -1,4 +1,4 @@
-# sys_random_h.m4 serial 4
+# sys_random_h.m4 serial 5
 dnl Copyright (C) 2020 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -25,7 +25,8 @@ AC_DEFUN([gl_HEADER_SYS_RANDOM],
   dnl corresponding gnulib module is not in use.
   gl_WARN_ON_USE_PREPARE([[
 #if HAVE_SYS_RANDOM_H
-/* Additional includes are needed before <sys/random.h> on Mac OS X.  */
+/* Additional includes are needed before <sys/random.h> on uClibc
+   and Mac OS X.  */
 # include <sys/types.h>
 # include <stdlib.h>
 # include <sys/random.h>