iOS Support

[rollerozxa]

Principia used to be available on iOS but was never updated from 1.4.0.5 and as such drifted off from the rest of the platforms. Especially now it is in a dire state, both not being maintained after 1.5 and not touched for 8 years of iOS updates.

This issue serves to track a list of things that would need to be resolved before Principia would be able to support iOS again, for anyone who would be interested in it.

• Implement and update new dialogs, as it lacks anything from 1.5 and 1.5.1.
• Get the project files to work with the modern iOS development tools. (Principia was targetting around iOS 6-8 at the time, there's probably been a lot of changes that have built up since then)
• Compile as 64-bit. (32-bit support has been removed in iOS 11)
• OpenGLES is currently deprecated in iOS but as far as I know not completely removed. That might become an issue if it's completely dropped in favour of Metal, though there is MetalANGLE that could provide compatibility if it is dropped.
• Provide dependencies that have been removed from the source tree during the open source development (cURL, Freetype, libpng and libjpeg). Something like the dependency build pipeline for Android would be useful.

[griffi-gh]

1) do ios builds work at all currently (even if outdated)?
2) how are we going to test it?
we need someone with an iphone (either jailbroken/altstore/testflight)

preferably the game should be tested on at least two major ios versions (latest + the oldest supported version)

[rollerozxa]

I've removed the iOS build directory from master for now since I don't see it being worked on or being fixed up for quite some time from now.

For anyone in the future willing to go through the process of porting, you can grab build-ios/ from 7afaa385b3ba39f43ee72b590b2b3d31820b2bee in the Git history to work on.

Any other iOS-specific code behind preprocessor statements should be kept.