Updated VM statistics patch

[Marcelo Tosatti]

Hi, 

I've updated the VM statistics patch. The following changed:

- Added CONFIG_VM_STATS option and Configure.help documentation
- Added Documentation/vm/statistics file which has a description
  of each stats field.
- Added more statistics:

vm_pgagescan: pages scanned by refill_inactive_scan()
vm_pgagedown: pages aged down by refill_inative_scan()
vm_pgageup: pages aged up by refill_inactive_scan()/try_to_swap_out()
vm_pgdeactfail_age: nr of deactivation failures on refill_inactive_scan()
due to >0 age
vm_pgdeactfail_ref: nr of deactivation failures on refill_inactive_scan()
due to zero aged pages with more users than the pagecache
vm_ptescan: nr of present ptes scanned by swap_out()
vm_pteunmap: nr of present ptes unmapped by swap_out()

- Changed the vmstat.c hack to not report separated per-zone information
by default, making the output more readable. If needed the per-zone
information can be seen with the "-z" option. 

Kernel patch (vmstatistics.patch) plus vmstat patch (vmstat.patch) plus
vmstat.c itself at 
http://bazar.conectiva.com.br/~marcelo/patches/v2.4/2.4.7pre5/