Support using INET as primary key

[digizeph]

Currently, we cannot create a table with INET field as primary key or unique constraint, and thus preventing us from doing things like upsert based on IP addresses in a table.

D create table if not exists test ( ip INET, PRIMARY KEY (ip));
Invalid type Error: Invalid Type [INET]: Invalid type for index key.

Would love to have this feature added in the future. Thanks!