The vs_get_data function finds the value of a pointer to data for a given VirtualServer* and slot. The slot must be a slot number returned from vs_alloc_slot or vs_set_data.
void* vs_get_data(const VirtualServer* vs, int slot);
The value of the pointer previously stored via vs_set_data, or NULL on failure.
const VirtualServer* vs represents the virtual server to query the pointer for.
int slot is the slot number to retrieve the pointer from.