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/meson.build

@@ -3,6 +3,9 @@ project('scrcpy-app', 'c')
 src = [
     'src/scrcpy.c',
     'src/command.c',
+    'src/control.c',
+    'src/controlevent.c',
+    'src/convert.c',
     'src/decoder.c',
     'src/frames.c',
     'src/lockutil.c',
@@ -26,3 +29,17 @@ dependencies = [
 ]
 
 executable('scrcpy', src, dependencies: dependencies)
+
+
+### TESTS
+
+tests = [
+    ['test_control_event_queue', ['tests/test_control_event_queue.c', 'src/controlevent.c']],
+]
+
+src_dir = include_directories('src')
+
+foreach t : tests
+    exe = executable(t[0], t[1], include_directories: src_dir, dependencies: dependencies)
+    test(t[0], exe)
+endforeach