- Implement pm_suspend(), which is callable from anywhere in the kernel, 
  and takes one of 

  	PM_SUSPEND_STANDBY
	PM_SUSPEND_MEM
	PM_SUSPEND_DISK

  and enters the appropriate state. 

- Change sysfs file to look for 

  "standby"
  "mem"
  "disk"

  for what state to enter (rather than 'suspend' and 'hibernate' for the 
  latter two). 

- Add pm_sem to block multiple suspend sequences happening at once. 

- Allocate a console and stop processes from common code before entering
  state.

- Add pm_power_down() callback for platform drivers to implement. Will be 
  called to actually enter the low-power state.