Ei protocol support

- Use the configured keyboard layout, track ei seats to reconfigure their keyboards
- DBus interface
- Disambiguate input devices per backend instance
- Add support for `ei_keysym` and `ei_text`
- Act as input method for ei_text UTF-8 injection
- Create a region per output for abosolute pointer position
- Map ei region for touchscreen emulation
- Release pointer buttons and keys on removal
- Send modifiers to EI connections

src/backend/x11.rs

@@ -534,14 +534,14 @@ impl State {
             let device = event.device();
             for seat in self.common.shell.read().seats.iter() {
                 let devices = seat.user_data().get::<Devices>().unwrap();
-                if devices.has_device(&device) {
+                if devices.has_device(&device, &crate::input::InputBackendId::Normal) {
                     seat.set_active_output(&output);
                     break;
                 }
             }
         };
 
-        self.process_input_event(event);
+        self.process_input_event(event, crate::input::InputBackendId::Normal);
         // TODO actually figure out the output
         for output in self.common.shell.read().outputs() {
             self.backend.x11().schedule_render(output);