Drop CIrrDeviceLinux in favor of SDL

[numberZero]

Parent issue: #157

Required:

• Clipboard [nosquash] Implement X11 primary selection, and add clipboard support for SDL #132
• Icon SDL: Support setting window icon at runtime #172 + Minetest side

Optional:

• HiDPI SDL: Support high DPI minetest#14549 + Minetest side
  (broken currently as pre-XRandR stuff always returns 96 dpi nowadays)

[Lazerbeak12345]

I noticed that the two check-boxes have been completed (but not synced here). Any further status updates? (not nagging- just low-key looking for something I can help with if it's within my ability)