ASLTS: Update bdemo/0241 test to expect two errors, not just one.

Change in ACPICA behavior after DeRefOf fix.
DeRefOf operator: Update to fully resolve FieldUnit and BufferField refs.

Previously, references to these objects were resolved only to the actual
FieldUnit or BufferField object. The correct behavior is to resolve these
references to an actual value.

NOTE: It appears that this issues is present in Windows7 but not
Windows8.