remove whole-process swapping
Long before Unix supported paging, it used process swapping to reclaim
memory.  The code is there and in theory it runs when we get *extremely* low
on memory.  In practice, it never runs since the definition of low-on-memory
is antiquated. (XXX: define what antiquated means)
You can check the number of swapout/swapin events with kstats:
$ kstat -p ::vm:swapin ::vm:swapout

*** 221,231 ****
          label_t pcb = t->t_pcb;
  
          (void) setjmp(&t->t_pcb);
          t->t_flag |= T_PANIC;
  
-         t->t_schedflag |= TS_DONT_SWAP;
          t->t_bound_cpu = cp;
          t->t_preempt++;
  
          panic_enter_hw(s);
  
--- 221,230 ----