ACPICA: Sleep/Wake interfaces: optionally execute _GTS and _BFS

Enhanced the sleep/wake interfaces to optionally execute the
_GTS method (Going To Sleep), and the _BFS method (Back From
Sleep).  Windows apparently does not execute these methods, and
therefore these methods are often untested. It has been seen on
some systems where the execution of these methods causes errors
and also prevents the machine from entering S5. It is therefore
suggested that host operating systems do not execute these methods
by default. In the future, perhaps these methods can be optionally
executed based on the age of the system and/or what is the newest
version of Windows that the BIOS asks for via _OSI.

Signed-off-by: Lin Ming <ming.m.lin@intel.com>
Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>