Separate the enums from cam/cam.h

The settings.h file doesn't actually need all of the definitions
on cam.h, only some of the enums. They can, therefore, be separated
into another file, which is included by settings.h instead.
The other changes are fixing files that included settings.h and
depended on indirect includes from includes of includes of cam.h

src/core/announce_multiplayer_session.cpp

@@ -3,6 +3,7 @@
 // Refer to the license.txt file included.
 
 #include <chrono>
+#include <future>
 #include <vector>
 #include "announce_multiplayer_session.h"
 #include "common/announce_multiplayer_room.h"