kernel - Add shared active virtual memory, i386

kernel - Add shared active virtual memory, i386

* Add shared active virtual memory.

  Shared active real memory represents the amount of memory shared across
  two or more pmap instances.  The memory is counted just once.

  Shared active virtual memory multiplies that value out by the number
  of pmap instances the memory is being shared across, giving the sysop
  some idea of the amount of ram being saved by e.g. shared libraries or
  shared mmap()s, etc.

* Collect statistics on 32-bit systems too.