Syntax helpers for IPC RPC

[NikVolf]

• is almost only for code generation, so that incoming stream would dispatch to ipc interface methods without any extra code
• the only file of interest should be ipc/codegen/codegen.rs and tests/example.rs
• IpcInterface itself is subject to change and non-essential in the current state (just a draft)
• further optimizations should come to reduce mem copies
• only handles method invocation made by value (no &)
• transport agnostic
• different serialization methods can be easily replaced/added during compile time with example at tests/build.rs

[gavofyork]

horrible whitespacing for a few lines here.