multimedia/kodi-devel: Enable GBM and WAYLAND by default

• Lift the previous restriction of only being able to build for a single platform.
• The 'kodi' script will run the appropriate platform binary based on environment variables (DISPLAY, WAYLAND_DISPLAY), so this unlocks the ability to run Kodi in more environments, i.e., under Xorg, the console, or in Wayland compositors.
• Export XKB_DEFAULT_RULES=evdev in the 'kodi' script to avoid surprises where keyboard input does not work correctly.
• Add explicit xkeyboard-config run dependency. It is already implicit for X11 via xorg-server and required for correctly working input with WAYLAND and GBM.
• GBM: Workaround a compatibility problem between Kodi and our libepoll-shim and unbreak input
• Remove slave port scaffolding
• Remove a no longer needed patch