Wrap SDL thread functions into scrcpy-specific API

The goal is to expose a consistent API for system tools, and paves the
way to make the "core" independant of SDL in the future.

app/src/controller.h

@@ -4,21 +4,20 @@
 #include "common.h"
 
 #include <stdbool.h>
-#include <SDL2/SDL_mutex.h>
-#include <SDL2/SDL_thread.h>
 
 #include "control_msg.h"
 #include "receiver.h"
 #include "util/cbuf.h"
 #include "util/net.h"
+#include "util/thread.h"
 
 struct control_msg_queue CBUF(struct control_msg, 64);
 
 struct controller {
     socket_t control_socket;
-    SDL_Thread *thread;
-    SDL_mutex *mutex;
-    SDL_cond *msg_cond;
+    sc_thread thread;
+    sc_mutex mutex;
+    sc_cond msg_cond;
     bool stopped;
     struct control_msg_queue queue;
     struct receiver receiver;