This was happening for async (response-less) messages, since they were
returning void and were were always just wrapping the return type in
an OwnPtr no matter what.
- Add IEndpoint::handle(IMessage), a big switch table on message type.
handle() will return a response message for synchronous messages,
and return nullptr otherwise.
- Use i32 instead of int for everything
- Make IMessage::encode() const
- Make IEndpoint::decode_message() static, this allows template code to
decode messages without an endpoint instance on hand.
Each message will now have a typedef called ResponseType as an alias
for the expected response type. This will aid in implementing the sync
messaging code.
Instead of doing everything manually in C++, let's do some codegen.
This patch adds a crude but effective IPC definition parser, along
with two initial definition files for the AudioServer's client and
server endpoints.
