Do nothing special for arc4random_addrandom(), arc4random_pushb(),
arc4random_pushk(), arc4random_stir(), they are not implemented in
OpenBSD libc.

Replace the pure Perl arc4random_bytes(), arc4random_uniform()
implementation with arc4random_buf(3), arc4random_uniform(3) Perl
XS wrapper for OpenBSD libc functions.

--- lib/BSD/arc4random.pm.orig	Mon Jun  6 01:19:28 2011
+++ lib/BSD/arc4random.pm	Wed Oct 12 17:34:11 2016
@@ -1,5 +1,6 @@
 # $MirOS: contrib/hosted/tg/code/BSD::arc4random/lib/BSD/arc4random.pm,v 1.10 2011/06/05 23:19:04 tg Exp $
 #-
+# Copyright (c) 2016 Alexander Bluhm <bluhm@openbsd.org>
 # Copyright (c) 2008, 2009, 2010, 2011
 #	Thorsten Glaser <tg@mirbsd.org>
 # Copyright (c) 2009
@@ -73,35 +74,24 @@ arc4random()
 sub
 arc4random_addrandom($)
 {
-	my $buf = shift;
-
-	lock($arcfour_lock) if $have_threadlock;
-	return &arc4random_addrandom_xs($buf);
+	goto &arc4random;
 }
 
 sub
 arc4random_pushb($)
 {
-	my $buf = shift;
-
-	lock($arcfour_lock) if $have_threadlock;
-	return &arc4random_pushb_xs($buf);
+	goto &arc4random;
 }
 
 sub
 arc4random_pushk($)
 {
-	my $buf = shift;
-
-	lock($arcfour_lock) if $have_threadlock;
-	return &arc4random_pushk_xs($buf);
+	goto &arc4random;
 }
 
 sub
 arc4random_stir()
 {
-	lock($arcfour_lock) if $have_threadlock;
-	&arc4random_stir_xs();
 	return;
 }
 
@@ -109,80 +99,18 @@ sub
 arc4random_bytes($;$)
 {
 	my ($len, $buf) = @_;
-	my $val;
-	my $vleft = 0;
-	my $rv = '';
-	my $idx = 0;
 
-	if (defined($buf)) {
-		$val = arc4random_pushb($buf);
-		$vleft = 4;
-	}
-	while (($len - $idx) >= 4) {
-		if ($vleft < 4) {
-			$val = arc4random();
-			$vleft = 4;
-		}
-		vec($rv, $idx / 4, 32) = $val;
-		$idx += 4;
-		$vleft = 0;
-	}
-	while ($idx < $len) {
-		if ($vleft == 0) {
-			$val = arc4random();
-			$vleft = 4;
-		}
-		vec($rv, $idx, 8) = $val & 0xFF;
-		$idx++;
-		$val >>= 8;
-		$vleft--;
-	}
-	return $rv;
+	lock($arcfour_lock) if $have_threadlock;
+	return &arc4random_buf_xs($len);
 }
 
-# Perl implementation of arc4random_uniform(3)
-# C implementation contributed by djm@openbsd.org, Jinmei_Tatuya@isc.org
-#
-# Calculate a uniformly distributed random number less than upper_bound
-# avoiding "modulo bias".
-#
-# Uniformity is achieved by generating new random numbers until the one
-# returned is outside the range [0, 2**32 % upper_bound).  This
-# guarantees the selected random number will be inside
-# [2**32 % upper_bound, 2**32) which maps back to [0, upper_bound)
-# after reduction modulo upper_bound.
-
 sub
 arc4random_uniform($)
 {
 	my $upper_bound = shift;
-	my $r;
-	my $min;
 
-	return 0 unless defined($upper_bound);
-	# convert upper_bound to 32-bit UV (unsigned integer value)
-	$upper_bound &= 0xFFFFFFFF;
-	return 0 if $upper_bound < 2 || $upper_bound > 0xFFFFFFFF;
-
-	# Calculate (2**32 % upper_bound) avoiding 64-bit math
-	if ($upper_bound > 0x80000000) {
-		# 2**32 - upper_bound (only one "value area")
-		$min = 1 + (~$upper_bound & 0xFFFFFFFF);
-	} else {
-		# (2**32 - x) % x == 2**32 % x when x <= 2**31
-		$min = (0xFFFFFFFF - $upper_bound + 1) % $upper_bound;
-	}
-
-	# This could theoretically loop forever but each retry has
-	# p > 0.5 (worst case, usually far better) of selecting a
-	# number inside the range we need, so it should rarely need
-	# to re-roll.
-	while (1) {
-		$r = arc4random();
-		last if $r >= $min;
-	}
-
-	return ($r % $upper_bound);
+	lock($arcfour_lock) if $have_threadlock;
+	return &arc4random_uniform_xs($upper_bound);
 }
 
 # private implementation for a tied $RANDOM variable