iASL: Emit remark for unreferenced objects declared in methods.

Adds support to detect names that are declared within a control method,
but are unused (these are temporary names that are only valid during
the time the method is executing). A remark is issued for these cases.
ACPICA BZ 1022.
iASL: Improve behavior of the -p (path prefix) option.

This change allows for zero or multiple periods (dots) within the
prefix pathname.

Also converts backslashes to forward slashes.
ACPICA BZ 1060.