Legacy Rust syc

Legacy Rust syc (v0.1.x)

The first syc: a streaming archiver in (almost) pure Rust, with zstd, LZMA and PPMd7 backends, packJPG/packPNG image pre-compression, dedup (whole-file and FastCDC), LZP and delta pre-filters, append frames and split archives. Its last release is v0.1.29 (Linux x86-64, Windows x86-64, Windows 7 32-bit).

It is kept, unchanged, in legacy/rust/: its README (usage and switches) and NOTES.md (its development log and benchmarks against FreeArc) in the open, and its sources archived in syc-rust-v0.1.29.zip so they don't read as the current code.

cd legacy/rust
unzip syc-rust-v0.1.29.zip
cargo build --release

Known issue: 25 roundtrip integration tests fail since v0.1.27, which keeps the source basename in entry paths; the tests predate it.