C99 migration, boring refactorings

[a1batross]

I don't think anything stops us from migrating to proper C99.

At least we get designated initializers (which I think I already used somewhere in the engine, but can't remember where) and finally use __func__.

[SNMetamorph]

Oh, It finally happened 🎉

[mittorn]

What you give: uncounted legacy compiler support What you'll get: {._=0;}