CPCEC, ZXSEC and CSFEC

What's New:

- minor patch fixing a bug where the disc file handler in all emus would not fall back to read-only modes when inserting read-only files in non-read-only modes (reported by Dlfrsilver). Removed the "microwave static" mode, it never looked right; instead, the user can now independently set whether Gigascreen and X-blending are fine or coarse.