allow users to enable access to the /dev/crypto, but keep it turned off

by default, adjust comments in sysctl.conf;  ok markus, tedu, djm, miod

src/etc/sysctl.conf

@@ -1,4 +1,4 @@
-#	$OpenBSD: sysctl.conf,v 1.48 2010/11/26 12:24:14 otto Exp $
+#	$OpenBSD: sysctl.conf,v 1.49 2011/02/16 10:37:45 mikeb Exp $
 #
 # This file contains a list of sysctl options the user wants set at
 # boot time.  See sysctl(3) and sysctl(8) for more information on
@@ -29,7 +29,8 @@
 #vm.swapencrypt.enable=0	# 0=Do not encrypt pages that go to swap
 #vfs.nfs.iothreads=4		# Number of nfsio kernel threads
 #net.inet.ip.mtudisc=0		# 0=Disable tcp mtu discovery
-#kern.usercrypto=0		# 0=Disable userland use of /dev/crypto
+#kern.usercrypto=1		# 1=Enable userland use of /dev/crypto
+#kern.userasymcrypto=1		# 1=Permit userland to do asymmetric crypto
 #kern.splassert=2		# 2=Enable with verbose error messages
 #kern.nosuidcoredump=2		# 2=Put suid coredumps in /var/crash
 #kern.watchdog.period=32	# >0=Enable hardware watchdog(4) timer if available