primitive aliases used before definitions are not handled properly

[rooooooooob]

example:

pool_params = ( operator:       pool_keyhash
              , vrf_keyhash:    vrf_keyhash
              , pledge:         coin
              , cost:           coin
              , margin:         unit_interval
              , reward_account: reward_account
              , pool_owners:    set<addr_keyhash>
              , relays:         [* relay]
              , pool_metadata:  pool_metadata / null
              )

coin = uint

will cause the coin: coin in pool_params to be treated as RustType::Rust(RustIdent("Coin")) instead of RustType::Alias(AliasIdent::Rust(RustIdent("Coin")), RustType::Primitive(Primitive::U64)) which results in to/from wasm generating incorrect code as it thinks it's a rust struct not a primitive. This is a problem as it will try and take it by reference (important since &u64 params are compile errors in wasm_bindgen) and will clone it excessively (less important).

This would likely be fixed by #93