Fuzz this

[killercup]

Adding fuzz targets for all the functions that take byte slices is an easy way to assert that they don't panic unexpectedly. Even if it's unlikely to find buffer overflows or use after free in Rust code, in my experience there are at least one or two integer overflows that a fuzzer can find :)

cf. https://rust-fuzz.github.io/book/introduction.html for how to fuzz Rust libraries