Ensure smaps exists before we asume vm_accuracy=2

  I've first used this script on GRsecurity enabled kernels
  which tweak kernel to not provide `/proc/<PID>/smaps` due
  to some security concerns.

  Reading through the source it seems that code was blindly
  presuming there should be precise vm_accounting available
  when in reality it falls back to accounting based on figures
  from `/proc/<PID>/statm` which lead to skewed stats for multi
  process services such as httpd, spamd.