machdep.kbdreset enables a shutdown by Ctrl-Alt-Del on amd64 and

i386.  Stop abusing it on other archs for controling a shutdown by
pressing the soft power button:
* Add a MI sysctl hw.allowpowerdown; if set to 1 (the default) it
allows a power button shutdown.
* Make acpi(4)/acpibtn(4) honor hw.allowpowerdown.
* Switch the various power button intercepts on landisk, sgi, sparc64
and zaurus over to hw.allowpowerdown.
* Garbage collect the machdep.kbdreset sysctl on all archs other than
amd64 and i386.
ok miod@

src/etc/etc.landisk/sysctl.conf

@@ -1,2 +1 @@
-#machdep.kbdreset=1		# permit console to do a nice halt
 #machdep.led_blink=1		# blink the power led

src/etc/etc.loongson/sysctl.conf

@@ -1 +0,0 @@
-#machdep.kbdreset=1		# 1=Enable power button shutdown

src/etc/etc.palm/sysctl.conf

@@ -1,4 +1,3 @@
-#machdep.kbdreset=1		# permit zkbd(4) power key to do a nice halt
 #machdep.maxspeed=520		# set change maximum processor speed
 #machdep.lidsuspend=1		# closing the lid will suspend machine
 #hw.setperf=0			# 0=slowest speed, 100=fastest speed

src/etc/etc.sgi/sysctl.conf

@@ -1 +0,0 @@
-#machdep.kbdreset=1		# 1=Enable power button shutdown

src/etc/etc.sparc64/sysctl.conf

@@ -1,3 +1,2 @@
 #machdep.led_blink=1		# 1=On sparc64, make led(s) blink
 #machdep.allowaperture=1	# See xf86(4)
-#machdep.kbdreset=1		# permit console to do a nice halt

src/etc/etc.zaurus/sysctl.conf

@@ -1,4 +1,3 @@
-#machdep.kbdreset=1		# permit zkbd(4) power key to do a nice halt
 #machdep.maxspeed=520		# set change maximum processor speed
 #machdep.lidsuspend=1		# closing the lid will suspend machine
 #hw.setperf=0			# 0=slowest speed, 100=fastest speed

src/etc/sysctl.conf

@@ -1,4 +1,4 @@
-#	$OpenBSD: sysctl.conf,v 1.51 2011/04/04 11:14:33 deraadt Exp $
+#	$OpenBSD: sysctl.conf,v 1.52 2011/06/24 19:47:48 naddy 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
@@ -36,3 +36,4 @@
 #kern.watchdog.period=32	# >0=Enable hardware watchdog(4) timer if available
 #kern.watchdog.auto=0		# 0=Disable automatic watchdog(4) retriggering
 #kern.pool_debug=0		# 0=Disable pool corruption checks (faster)
+#hw.allowpowerdown=0		# 0=Disable power button shutdown