Improve powerd accuracy on SMP based systems.  We're now using summary load instead of average load.

powerd is independant from number and size of frequency levels now.

Add new hiadaptive load for ac powered systems which rises freq twice as fast and drops it on 1/8 per time interval.

Default polling was changed from 1/2 to 1/4 of a second.

Based upon FreeBSD 7.2 patches to powerd.