Fixed compile warnings about unused variables.

Found by buildbot.

src/audio/emscripten/SDL_emscriptenaudio.c

@@ -62,7 +62,6 @@ HandleAudioProcess(_THIS)
     int byte_len = 0;
     int bytes = SDL_AUDIO_BITSIZE(this->spec.format) / 8;
     int bytes_in = SDL_AUDIO_BITSIZE(this->convert.src_format) / 8;
-    int i;
 
     /* Only do soemthing if audio is enabled */
     if (!this->enabled)

src/joystick/emscripten/SDL_sysjoystick.c

@@ -335,7 +335,7 @@ SDL_SYS_JoystickUpdate(SDL_Joystick * joystick)
 {
     EmscriptenGamepadEvent gamepadState;
     SDL_joylist_item *item = SDL_joylist;
-    int i, result, button, buttonState;
+    int i, result, buttonState;
 
     while (item != NULL) {
         result = emscripten_get_gamepad_status(item->index, &gamepadState);