Add alloc function

[selenil]

No description provided.

[DynamicCake]

I don't think this should be merged.

I don't like it since the alloc function doesn't do anything on non table/userdata values and silently does nothing.
I think instead, we should just provide alternative functions for tables and userdata for that can alloc and not alloc.

[DynamicCake]

I think this should be closed because of #20