Implement keyboard/mouse control

To control the device from the computer:
 - retrieve mouse and keyboard SDL events;
 - convert them to Android events;
 - serialize them;
 - send them on the same socket used by the video stream (but in the
 opposite direction);
 - deserialize the events on the Android side;
 - inject them using the InputManager.

app/src/control.h

@@ -0,0 +1,29 @@
+#ifndef CONTROL_H
+#define CONTROL_H
+
+#include "controlevent.h"
+
+#include <SDL2/SDL_mutex.h>
+#include <SDL2/SDL_net.h>
+#include <SDL2/SDL_stdinc.h>
+
+struct controller {
+    TCPsocket video_socket;
+    SDL_Thread *thread;
+    SDL_mutex *mutex;
+    SDL_cond *event_cond;
+    SDL_bool stopped;
+    struct control_event_queue queue;
+};
+
+SDL_bool controller_init(struct controller *controller, TCPsocket video_socket);
+void controller_destroy(struct controller *controller);
+
+SDL_bool controller_start(struct controller *controller);
+void controller_stop(struct controller *controller);
+void controller_join(struct controller *controller);
+
+// expose simple API to hide control_event_queue
+SDL_bool controller_push_event(struct controller *controller, struct control_event *event);
+
+#endif