Delay effect retriggers instrument

This should really be handled in a different way, but let's leave that
for a full player engine rewrite.

Signed-off-by: Claudio Matsuoka <cmatsuoka@gmail.com>
FT2 resets note release on new instrument only

New note events should not reset note release in FT2. See forgotten city.xm
at position 12, channel 19.

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

Signed-off-by: Claudio Matsuoka <cmatsuoka@gmail.com>
Don't overwrite existing track data

Signed-off-by: Claudio Matsuoka <cmatsuoka@gmail.com>
Amend e9d08e to retain behavior if no envelope

Previous behavior of FT2 new note without instrument is valid if the
instrument has volume envelope disabled (Last Battle.xm). If there's
a volume envelope, don't reset NOTE_FADEOUT.

Signed-off-by: Claudio Matsuoka <cmatsuoka@gmail.com>
Merge branch 'master' of github.com:cmatsuoka/libxmp