Fix build errors with Wayland on Debian 13 (trixie) using Clang 16

[pkgdemon]

This pull request resolves several build errors encountered when compiling with Wayland support (./configure --enable-server=wayland) on Debian 13 Testing (codename trixie) using Clang version 16.0.6.

The updates include:

• Selector Naming Issues: Corrected method declarations to properly align with Objective-C selector conventions.
• Function Pointer Compatibility: Fixed mismatched function pointer types to align with expected signatures.
• Implicit Declarations: Added necessary includes and declarations for Wayland functions to prevent implicit declaration errors.
• Type Corrections: Adjusted type usage to match expected formats and avoid type mismatch errors.

If this PR is accepted, I will work on a follow-up PR will address additional build issues on Arch Linux with Clang 18.1.8.

[fredkiefer]

Looks good to me. Could you please check the few comments I left, then it's fine to merge this.

[pkgdemon]

Also just wanted to leave a note to correct a statement made in my description. The build is working now with Arch Linux and clang 18. No additional PR will be needed for that.