Rename "event" to "message"

After the recent refactorings, a "control event" is not necessarily an
"event" (it may be a "command"). Similarly, the unique "device event"
used to send the device clipboard content is more a "reponse" to the
request from the client than an "event".

Rename both to "message", and rename the message types to better
describe their intent.

app/src/convert.h

@@ -4,7 +4,7 @@
 #include <stdbool.h>
 #include <SDL2/SDL_events.h>
 
-#include "control_event.h"
+#include "control_msg.h"
 
 struct complete_mouse_motion_event {
     SDL_MouseMotionEvent *mouse_motion_event;
@@ -18,24 +18,24 @@ struct complete_mouse_wheel_event {
 
 bool
 input_key_from_sdl_to_android(const SDL_KeyboardEvent *from,
-                              struct control_event *to);
+                              struct control_msg *to);
 
 bool
 mouse_button_from_sdl_to_android(const SDL_MouseButtonEvent *from,
                                  struct size screen_size,
-                                 struct control_event *to);
+                                 struct control_msg *to);
 
 // the video size may be different from the real device size, so we need the
 // size to which the absolute position apply, to scale it accordingly
 bool
 mouse_motion_from_sdl_to_android(const SDL_MouseMotionEvent *from,
                                  struct size screen_size,
-                                 struct control_event *to);
+                                 struct control_msg *to);
 
 // on Android, a scroll event requires the current mouse position
 bool
 mouse_wheel_from_sdl_to_android(const SDL_MouseWheelEvent *from,
                                 struct position position,
-                                struct control_event *to);
+                                struct control_msg *to);
 
 #endif