Suppress deprecation warnings

[jasonbobier]

• I confirm that I am the author of this code and release it to the SDL project under the zlib license. This contribution does not contain code from other sources, including code generated by a Large Language Model ("AI").

Note that the code is written (well copied and pasted all over :)) by me, but the comments are a mix of my comments and what Claude told me to make sure that I was giving accurate notes.

Description

Wrapped the deprecation warnings in:
clang diagnostic ignored "-Wdeprecated-declarations"

Also added swiftpm related directories to the .gitignore in preparation for another PR.

NOTE: This only hides the warnings to clean up the build. It does not attempt to modernize the calling sites. I looked at that as well, but because of support back to 10.13, many of the sites couldn't be fully modernized.

Existing Issue(s)

[slouken]

@icculus, do we actually want to silence these deprecation warnings?

[jasonbobier]

I would argue that you do because they are noise that hide actual warnings. These aren't real warnings because you are supporting OS versions that require the code that cause the warnings. Hiding each individually means that it is easy to search for them later whenever you update your minimum OS requirements. And a warning free build should always be the end goal imo.

[icculus]

Yeah, I'm pretty sure these are all fallbacks where we have a more modern approach in place for newer systems.

Gonna go over all of these though, to make sure we can't just delete a few of them. What is the minimum macOS at this point?