Fix XM finetune handling

Signed-off-by: Claudio Matsuoka <cmatsuoka@gmail.com>
[test] Add OpenMPT XM finetune test case

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

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