Mention that linux and linux32 emulations are not loaded automatically

for modular kernels, and mention how to enable that. Bump date.

share/man/man8/compat_linux.8

@@ -1,4 +1,4 @@
-.\"	$NetBSD: compat_linux.8,v 1.38 2017/07/03 21:31:00 wiz Exp $
+.\"	$NetBSD: compat_linux.8,v 1.39 2017/09/29 21:48:17 wiz Exp $
 .\"
 .\" Copyright (c) 1995 Frank van der Linden
 .\" All rights reserved.
@@ -29,7 +29,7 @@
 .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 .\"
-.Dd April 30, 2007
+.Dd September 29, 2017
 .Dt COMPAT_LINUX 8
 .Os
 .Sh NAME
@@ -393,9 +393,7 @@ for further information.
 .Ss Setting up other files
 Newer version of Linux use
 .Pa /etc/nsswitch.conf
-for network information, such as
-.Tn NIS
-and DNS.
+for network information, such as NIS and DNS.
 You must create or get a valid copy of this file and put it in
 .Pa /emul/linux/etc .
 .Ss Finding the necessary files
@@ -537,6 +535,17 @@ directory, namely:
 Be warned: the first link mentioned here makes SVGAlib binaries
 work, but may confuse others, so you may have to remove it again at
 some point.
+.Sh CAVEATS
+When using a modular kernel (see
+.Xr module 7 ) ,
+the linux and linux32 emulations are not loaded automatically (for
+security reasons).
+To enable autoloading, set the appropriate
+.Xr sysctl 8 Ap s :
+.Bd -literal
+sysctl -w emul.linux.enabled=1
+sysctl -w emul.linux32.enabled=1
+.Ed
 .Sh BUGS
 The information about Linux distributions may become outdated.
 .Pp