* Added syscalls _kern_set_cpu_enabled() and _kern_cpu_enabled().
* scheduler.c::sRunQueue::tail was not maintained at all; changed sRunQueue to
be a simple thread pointer instead of a struct thread_queue.
* Turns out we're monitoring CPU activity incorrectly when we've got more
than one CPU.
* Renamed the global CPU array from "cpu" to gCPU.
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@16186 a95241bf-73f2-0310-859d-f6bbb57e9c96