Fix for _INI regression introduced in version 20130328.

This change fixes a problem introduced in 20130328 where _INI methods
are no longer executed properly because of a memory block that is not
initialized correctly.

https://github.com/acpica/acpica/commit/637accd073a205eb4acac935f34d0eaee0c301a8
Import ACPICA 20130517.
Merge ACPICA 20130517.