[test] Use a more strict test for the UNIC loader

Signed-off-by: Claudio Matsuoka <cmatsuoka@gmail.com>
Retrieve old fadeout value in XM keyoff with instrument

Signed-off-by: Claudio Matsuoka <cmatsuoka@gmail.com>
Handle XM keyoff with delay

Signed-off-by: Claudio Matsuoka <cmatsuoka@gmail.com>
[test] Update reference data for OpenMPT delaycut.xm

Signed-off-by: Claudio Matsuoka <cmatsuoka@gmail.com>
[test] Add OpenMPT keyoff+instr.xm test case

Signed-off-by: Claudio Matsuoka <cmatsuoka@gmail.com>