[DRAFT] Move error and dpi types into a separate crate + split out x11 symbol loading code + xinerama & multihead support

[goddessfreya]

See https://github.com/rust-windowing/winit_types and https://github.com/rust-windowing/glutin_x11_sym.

@murarth @Osspial Are you folks familiar with how to setup CI for glutin_x11_sym, glutin_sys and winit_types?

Platforms:

• [x] X11
• [x] Wayland
• [x] Macos
• [x] Windows
• [x] iOS
• [x] Web

Other:

• [ ] Tested on all platforms changed
• [ ] Compilation warnings were addressed
• [ ] cargo fmt has been run on this branch
• [ ] cargo doc builds successfully
• [ ] Added an entry to CHANGELOG.md if knowledge of this change could be valuable to users
• [ ] Updated documentation to reflect any user-facing changes, including notes of platform-specific behavior
• [ ] Created or updated an example program if it would help users understand this functionality
• [ ] Updated feature matrix, if new features were added or implemented

[goddessfreya]

Hey @simlay, can you implement this for iOS? I couldn't get cargo check to work for iOS as it needed some SDK (which is of course macos only :/). Thanks :heart:

[simlay]

Sure! I’ll give it a whack!

[vbogaevsky]

Weren't we going to merge dpi_overhaul first?

[goddessfreya]

@vbogaevsky I don't think it particularly matters which order they land, does it? These changes don't really touch anything dpi related.

[Osspial]

@goddessfreya The DPI overhaul branch adds generics to the size and position types, and it'll be easier to manage this change if we delay merging this until after the generics have landed on master.

[daxpedda]

This is very old and needs to be remade completely.

Continues to be tracked in https://github.com/rust-windowing/winit/issues/2759.