ACPICA: Update for GCC 4

Fixes several issues with GCC 4.6 related to the new checks for
unused variables.

http://www.acpica.org/bugzilla/show_bug.cgi?id=935



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