ACPI: Avoid discarding a potential error value.

This is part of a new diagnostic I've managed to wire up
that finds all instances of "status_t" function return
values being discarded using attribute trickery and some
creative Clang pragmas. As you might guess, the resultant
errors list is absolutely gigantic, and most of them are
ones where the failure condition will never (that we care
about) be hit.

The ones in this commit likely are no-op changes, but
they were low-hanging fruit spotted while reviewing
the larger list. The next commit will bring more
substantial changes.

Embedded Controller, sync with FreeBSD

* Tries to handle all pending events at once
* Wait is now polling every mS while waiting

Remove remaining unnecessary 'volatile' qualifiers

acpi: switch acpi_object from a struct to a union

* this way the size of acpi_object_type matches the size of ACPI_OBJECT
for 32-bit and 64-bit builds.
* adjust users of the type acpi_object_type.

Fix compilation after rename and switch to cpp.

Simplify source file names and go from .c to .cpp

Remove remaining unnecessary 'volatile' qualifiers

acpi: switch acpi_object from a struct to a union

* this way the size of acpi_object_type matches the size of ACPI_OBJECT
for 32-bit and 64-bit builds.
* adjust users of the type acpi_object_type.

Fix compilation after rename and switch to cpp.

Simplify source file names and go from .c to .cpp