power(4) driver for the power switch on many landisk models, hooked

up to machdep.kbdreset; modelled after the sparc64 power(4) driver
discussed with miod@ and jsg@

src/etc/etc.landisk/sysctl.conf

@@ -0,0 +1 @@
+#machdep.kbdreset=1		# permit console to do a nice halt