Fix IT note fades, compressed stereo samples, approximate command \xx

[sagamusix]

If people keep using the library, might as well fix the most blatantly missing IT features to make modern IT tracks lightly more listenable: Compressed stereo samples and note fades. As a bonus, OpenMPT command \xx (Smooth MIDI Macro) is now imported as command Zxx (MIDI macro).

[sagamusix]

@sezero maybe you want to add these to your fork

[sezero]

@sezero maybe you want to add these to your fork

Thanks. There are conflicts though, will try resolving them.

[sezero]

@sezero maybe you want to add these to your fork

I resolved the conflicts (which were mostly due to Alice's fuzz fixes patchset)
and applied these patches. @AliceLR, @sagamusix: Do you see any brokenness
with sezero@bc39ec6, just in case?

[AliceLR]

I resolved the conflicts (which were mostly due to Alice's fuzz fixes patchset) and applied these patches. @AliceLR, @sagamusix: Do you see any brokenness with sezero@bc39ec6, just in case?

It looks like your patch shouldn't break the fuzz patch changes.

If people keep using the library

I think the license pretty much guarantees this—SDL_sound and SDL_mixer both use libmodplug explicitly because it's more permissive than their zlib license and they link it statically.

[sagamusix]

I think the license pretty much guarantees this—SDL_sound and SDL_mixer both use libmodplug explicitly because it's more permissive than their zlib license and they link it statically.

The fact that they (IIRC) use their own version ported to C doesn't make it any better 😭