Add #[allow(dead_code)] and #[allow(non_camel_case_types)] to the generated code

[acertain]

Generated code produces a large amount of non_camel_case_types and dead_code warnings, it should be marked allow so that rustc doesn't complain.

[dwrensha]

I understand the issue with the dead_code warning, but I'm puzzled about the non_camel_case_types warning. Could you post a schema whose generated code produces that warning?

The general problem is this: following Cargo's recommended method for generating code, I want to be able to use the include!() macro for bringing in the generated code, like this. Unfortunately, the include!() macro currently doesn't play nice with inner attributes: rust-lang/rust#18810

[tv42]

I've also needed to add all of these to where I have the include!:

#![allow(dead_code)]
#![allow(unused_qualifications)]
#![allow(clippy::expl_impl_clone_on_copy)]
#![allow(clippy::must_use_candidate)]
#![allow(clippy::semicolon_if_nothing_returned)]
#![allow(clippy::uninlined_format_args)]

[tv42]

The Rust issue linked has moved to rust-lang/rfcs#752

Since capnproto-rust generates files that mostly have a pub mod ... per top-level message and pub static for consts, maybe it should just generate those allows for each top-level thing. That doesn't sound too onerous.

[tv42]

Updated list of all the lint exceptions I've needed:

#![allow(clippy::as_conversions)]
#![allow(clippy::exhaustive_enums)]
#![allow(clippy::expl_impl_clone_on_copy)]
#![allow(clippy::match_same_arms)]
#![allow(clippy::module_name_repetitions)]
#![allow(clippy::must_use_candidate)]
#![allow(clippy::renamed_function_params)]
#![allow(clippy::semicolon_if_nothing_returned)]
#![allow(clippy::uninlined_format_args)]
#![allow(clippy::unreadable_literal)]
#![allow(clippy::unwrap_used)]
#![allow(clippy::used_underscore_binding)]
#![allow(dead_code)]
#![allow(unused_qualifications)]