Sync ACPICA with Intel's version
20150619.
* Replace various macros like ACPI_STRLEN with the standard C library
functions across the tree.
* Add support for OSDT table, to override existing namespace objects
from DSDT/SSDTs.
* Handle systems with two FACS tables better.
* Add a feature to allow for systems that do not contain an FACS.
* Fix wrong GUID strings for NFIT tables.
* Support for _CLS in AcpiGetObjectInfo().
* Update TCPA and TPM2 table definitions to a more recent TCG ACPI spec.
* Add definitions for the ACPI 6.0 GIC version field in MADT.
* Various fixes and enhancements in the tools.
For a more detailed list, please see sys/contrib/dev/acpica/changes.txt.