First-class Rust/Angora integration

[Shnatsel]

Angora is a new fuzzer that according to its authors is strictly superior to the AFL-inspired status quo. See https://arxiv.org/abs/1803.01307 for more info.

Angora itself is written in Rust, but does not support fuzzing Rust code yet, and does not have a good Cargo integration like afl, libfuzzer and honggfuzz do.

Tracking issue for supporting Rust in Angora: AngoraFuzzer/Angora#10
Tracking issue for higher-level Cargo integration: rust-fuzz/cargo-fuzz#165

Existing fuzzer integrations for reference:
https://github.com/rust-fuzz/cargo-fuzz
https://github.com/rust-fuzz/afl.rs
https://github.com/rust-fuzz/honggfuzz-rs

[Shnatsel]

It'd be great to support any fuzzers that show better results than the current ones in https://github.com/google/fuzzbench

At least one part of that should be fairly simple: rust-fuzz/afl.rs#167