document machdep.lidsuspend by example

src/etc/etc.amd64/sysctl.conf

@@ -1,2 +1,3 @@
 #machdep.allowaperture=2	# See xf86(4)
 #machdep.kbdreset=1		# permit console CTRL-ALT-DEL to do a nice halt
+#machdep.lidsuspend=1		# laptop lid closes cause a suspend

src/etc/etc.i386/sysctl.conf

@@ -1,6 +1,7 @@
 #machdep.allowaperture=2	# See xf86(4)
 #machdep.apmhalt=1		# 1=powerdown hack, try if halt -p doesn't work
 #machdep.kbdreset=1		# permit console CTRL-ALT-DEL to do a nice halt
+#machdep.lidsuspend=1		# laptop lid closes cause a suspend
 #machdep.userldt=1		# allow userland programs to play with ldt,
 				# required by some ports
 #kern.emul.aout=1		# enable running dynamic OpenBSD a.out bins