Support for .mmi (Mixed Media Image) for Genesis

[Proletar666]

https://www.gametechwiki.com/w/index.php/Pioneer_LaserActive

Sega Genesis add-on for this Pioneer LaserActive laserdisc home media player let one play games on LaserDiscs, a combined digital-analog disc format. Digital in-game graphics is rendered by console hardware of these add-ons on top of analog video. Here's the description:

https://techdocs.exodusemulator.com/Console/PioneerLaserActive/Laserdisc.html

The technical side of archiving process has finally been dealt with and now is considered polished enough:

https://techdocs.exodusemulator.com/Console/PioneerLaserActive/Archiving.html

The "Mixed media image" was developed for dumping these discs, this format combines digital content and captured raw uncompressed analog video signal into a single .mmi file (hence why huge sizes up to ~40GB per disc side), several games have already been dumped:

https://techdocs.exodusemulator.com/Console/PioneerLaserActive/Software.html

Currently, the author is adding support for Mega LD games in emulator Ares also on GitHub.

I ask to add support for this format to PicoDrive.

Duplicate on irixxxx's fork repo: https://github.com/irixxxx/picodrive/issues/193