WIP Register fst file format

[davidanthoff]

Don't merge yet, we first need to sort out various things in the upstream packages.

[timholy]

Are there really no magic bytes? In this case fst seems to mean several things:

• https://fileinfo.com/extension/fst
• http://whatis.techtarget.com/fileformat/FST-Linkable-program-dBFast
• https://github.com/fstpackage/fst

I bet you don't mean the first, but even knowing you I can't guess which of the other two you're hoping to support.

[davidanthoff]

I’m trying to find out. This will hopefully support the third format.

[davidanthoff]

Because we asked them to, they are actually adding a magic byte into the next version :) I'll follow up on this once everything is ready, will probably still be a while.

[timholy]

Open source at its finest!