Exposes an ABI for other languages; this is the new 'libimageflow'.
cargo test does the most, and tests correctness,
ruby imageflow_abi/src/test.rb (if the FFI gem is installed) will actually make FFI calls happen, in case you're skeptical of symbol name mangling et. al.
Run cargo doc --no-deps and look in target/doc
Run cargo build --release and look for target/release/libimageflow