Merging SDL2 and other stuff from my fork

[ahockersten]

Hey, as many are aware I've been maintaining a fork of Liero since quite some time.

The short backstory (as I remember it, 10+ years later), I originally wanted to add a single screen replay mode. Then I wanted SDL2 to address some performance issue when running Liero on high resolution screens and also to be able to add spectator mode. At the time gliptic wasn't very active so my changes ended up quite far from main. Then I had some inspiration and I added some more features. And some more changes. And so on... 😄

Anyways, there's never been a good reason for having two versions, so let's try to see if we can get whatever useful I have in.

Here's a brief outline of how I want to go about to accomplish this:

1. Resave all files in a "modern" editor.
   The line endings are messy and there are inconsistencies which makes it frustrating to work on the codebase in a modern editor. Unfortunately I have used some modern editors on my codebase and I was at times sloppy with how I committed stuff. It would be much easier to just avoid this. I can then rebase my fork on this, which should make the changes clearer.

2. Port all the changes that are needed to compile on modern systems
   That is, latest version of VS and CMake. I have CMake at least, unsure about VS but I think it uses CMake now.

3. Port single screen replay, SDL2 and spectator mode. These are a bit commingled so probably makes sense to do in one go.

4. ???
   We'll see when we get there what's left that seems relevant.

Unless I hear words otherwise I'll get started on looking further into this.

[grawlinson]

Merging the two codebases would be awesome. I’ll happily pull in any related changes. :)

[grawlinson]

Just setup a GitHub org for openliero, might be easier to go that route.

[ahockersten]

Sounds good! I'm closing this issue. I have more stuff that I want to get merged, but it's not really a part of this and deserves its own issues. Thanks!