fix CI

* Bump version to 6.0 (per semver check)
* Remove unused SIMD use statements
* hide a few warnings - these are TODOs, and should be fixed in separate PRs
* do NOT build SIMD as part of MSRV -- doesn't make any sense to combine nightly with MSRV

Release 5.0.0 with ffi-api disabled by default to avoid ODR issues

Bump to 4.0.0

new release

Update brotli decompressor crates and fix #91

remove warning

bump version

fix C encode api to allow nullptr + TakeOutput operation

bump version of brotli-decompressor to return Result<Write,Write> for…

… decompressor into_inner

tests for into_inner on both readers and writers