Add address map for better client index looking up

[gafferongames]

Some warnings need to be fixed, see above.

[gafferongames]

First issue. The map returns 0 if the client index isn't found, but client index of 0 is a valid index.

Please change that to return -1 if client index is found

[gafferongames]

Please change

define NETCODE_ADDRESS_MAP_BUCKETS 256

To be some function of the max clients, because as the max clients increases for the server, you will need more buckets.

(Maybe it should just be #define NETCODE_ADDRESS_MAP_BUCKETS NETCODE_MAX_CLIENTS? Then the size is n^2 on max clients... which is fine, and it handles worst case)

[gafferongames]

Please add a unit test for the map

[kienhg96]

Ok, I'll check them

[kienhg96]

I fixed the issues above, please have a check

[kienhg96]

I have added the create and destroy functions using allocator. I think you should wrap the allocator_context, allocate_function and free_function to a new struct called allocator. It could be much more convenient.

[gafferongames]

Merged. Thanks!