Introduce debug flags

While looking at phoc_server_setup i noticed that we should have

typedef enum PhocDebugFlags {
   PHOC_DEBUG_FLAG_DAMAGE_TRACKING,
   PHOC_DEBUG_FLAG_TOUCH_POINTS,
};

rather then passing individual booleans around. This makes further additions easier. We can then have things like

if (PHOC_DEBUG_TOUCH(server)) {
...
}