Add a /bin/top program for process table monitoring.

It automagically computes %CPU usage based on the number of times a process
has been scheduled between samples. The colonel task is used as idle timer.
This is pretty cool. :^)

Kernel/Scheduler.h

@@ -18,6 +18,7 @@ public:
     static bool yield();
     static bool context_switch(Process&);
     static void prepare_to_modify_tss(Process&);
+    static Process* colonel();
 private:
     static void prepare_for_iret_to_new_process();
 };