[Bug 40024] Prosound crashes on start

https://bugs.winehq.org/show_bug.cgi?id=40024

--- Comment #3 from Andrew Eikum  ---
I don't think I agree with the approach taking by the staging patchset. Instead
of refcounting to prevent access-after-free, we should just never access the
MIDIHDR after sending MOM_DONE to the application.

I'm not sure exactly how we can do this, but my approach would be to unmap the
MODM_LONGDATA header just before invoking MOM_DONE. Maybe we can do this in
mmsystem16.MMSYSTDRV_Callback3216. This would have the advantage of correctly
copying the flags that are set in midimap.modLongData to the 16-bit header. The
flags are currently not reaching the application in the MOM_DONE callback
invoked by midimap.modLongData.