Split adapter and wrapper into different entities

[blaubaer]

Motivation

I work on projects where I cannot use the Adapter(..) directly. I need to call the *.ServeHTTP(..) method directly.

Changes

1. This PR split the logic of the Adapter(..) and the included wrapper into different entities:
   • Adapter(..): Which will work as before (see tests)
   • ResponseWriterFactoryFactory.Create(..): Which is used to create a wrapped http.ResponseWriter from a given one, which is compressing (if requested).
2. Split some stuff from adapter.go into other files (like config.go and response_writer_factory.go)
3. Fixed go build flags to be 1.17+
4. Makes it possible to run all tests (but without cgo dependencies) if no cgo is available.
5. Some typo fixes
6. Added MinSizeRequestFunc(func(*http.Request) (int, error)) to be able to used instead of MinSize(..). Makes it able to determine minSize on each call of ResponseWriterFactoryFactory.Create(..) based on the request.
7. Added ErrorHandler(..) to be able to react to errors inside of the handling chain of httpcompression.
8. Introduced ErrHijackerNotSupported instead of enclosed error to be able to check for it directly.

[blaubaer]

@CAFxX is this project still alive?