Add i386 specific sysctl to modify halt -p processing, required to make

src/etc/etc.i386/sysctl.conf

@@ -1,3 +1,4 @@
 #machdep.allowaperture=1	# 1=permit access to aperture driver (XFree86)
 #machdep.apmwarn=10		# battery % when apm status messages enabled
+#machdep.apmhalt=0		# 1=powerdown hack, try if halt -p doesn't work
 #machdep.kbdreset=1		# permit console CTRL-ALT-DEL to do a nice halt