- Add prototypes for split-up swsusp functions that can be called from PM
  core: 

  save()
  write()
  read()
  restore()
  free()

- Base PM core algorithm on existence of these functions, and allow 
  graceful failure at each step. 

- Add pm_resume() function to be called on init to attempt to read swsusp
  image. 

- Add debugging. 

- Make sure we can handle all modes for suspend-to-disk.

- Add empty split-up functions to swsusp.