Remove miniz-sys, and map it to miniz_oxide for compatibility

.github/workflows/main.yml

@@ -37,13 +37,11 @@ jobs:
     - run: rustdoc --test README.md -L target/debug/deps --extern flate2=target/debug/libflate2.rlib --edition=2018
     - run: cargo test
     - run: cargo test --features zlib
-    - run: cargo test --features miniz-sys
     - run: cargo test --features zlib --no-default-features
     - run: cargo test --features zlib-ng-compat --no-default-features
       if: matrix.build != 'mingw'
     - run: cargo test --features cloudflare_zlib --no-default-features
       if: matrix.build != 'mingw'
-    - run: cargo test --features miniz-sys --no-default-features
 
   rustfmt:
     name: Rustfmt
@@ -54,15 +52,6 @@ jobs:
       run: rustup update stable && rustup default stable && rustup component add rustfmt
     - run: cargo fmt -- --check
 
-  systest:
-    name: Systest
-    runs-on: ubuntu-latest
-    steps:
-    - uses: actions/checkout@master
-    - name: Install Rust
-      run: rustup update stable && rustup default stable
-    - run: cargo run --manifest-path systest/Cargo.toml
-
   wasm:
     name: WebAssembly
     runs-on: ubuntu-latest

Cargo.toml

@@ -12,17 +12,12 @@ homepage = "https://github.com/rust-lang/flate2-rs"
 documentation = "https://docs.rs/flate2"
 description = """
 DEFLATE compression and decompression exposed as Read/BufRead/Write streams.
-Supports miniz_oxide, miniz.c, and multiple zlib implementations. Supports
-zlib, gzip, and raw deflate streams.
+Supports miniz_oxide and multiple zlib implementations. Supports zlib, gzip,
+and raw deflate streams.
 """
 
-[workspace]
-members = ['systest']
-
 [dependencies]
 libc = "0.2.65"
-cfg-if = "1.0.0"
-miniz-sys = { path = "miniz-sys", version = "0.1.11", optional = true }
 libz-sys = { version = "1.1.0", optional = true, default-features = false }
 cloudflare-zlib-sys = { version = "0.3.0", optional = true }
 miniz_oxide = { version = "0.5.0", optional = true, default-features = false }
@@ -42,3 +37,4 @@ zlib = ["any_zlib", "libz-sys"]
 zlib-ng-compat = ["zlib", "libz-sys/zlib-ng"]
 cloudflare_zlib = ["any_zlib", "cloudflare-zlib-sys"]
 rust_backend = ["miniz_oxide"]
+miniz-sys = ["rust_backend"] # For backwards compatibility

README.md

@@ -84,9 +84,6 @@ documentation](https://crates.io/crates/cloudflare-zlib-sys). Note that
 `cloudflare_zlib` will cause breakage if any other crate in your crate graph
 uses another version of zlib/libz.
 
-For compatibility with previous versions of `flate2`, the C version of `miniz.c`
-is still available, using the feature `miniz-sys`.
-
 # License
 
 This project is licensed under either of