Create a new blitter mode: 32bpp-sse2-anim, which is 32bpp-anim + this.
32bpp-sse2-anim is now used by default where 32bpp-anim would have been.
Also use this with the 32bpp-sse4-anim blitter.
See issue #6469.
MCI MIDI is poorly supported on newer versions of Windows and can cause large
delays at the beginning of tracks.
The new driver is based on a from-scratch reader for Standard MIDI Files. This
should be re-usable in other music drivers too, and can allow for finer control
of playback in general.
It also provides a better framework for reading MIDI data from other formats
than just SMF.
