Fix IT cut carry on note cut events

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

Signed-off-by: Claudio Matsuoka <cmatsuoka@gmail.com>
Minor refactor in IT read event

Signed-off-by: Claudio Matsuoka <cmatsuoka@gmail.com>
Fix IT envelope reset

Reset the envelope on a new instrument if previous envelope has finished.
See OpenMPT EnvReset.it test case.

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

Signed-off-by: Claudio Matsuoka <cmatsuoka@gmail.com>
Fix filter envelope reset

Filters with default cutoff shouldn't reset to full cutoff. See OpenMPT
test FilterEnvReset.it.

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

Signed-off-by: Claudio Matsuoka <cmatsuoka@gmail.com>
Fix sample change on compatible GXX mode

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

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

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