This patch splits up `tor_compress_memory_level()` into static functions
in the individual compression backends, which allows us to tune the
values per compression backend rather than globally.
See: https://bugs.torproject.org/21662
This patch adds support for checking if a given `compress_method_t` is
supported by the currently running Tor instance using
`tor_compress_supports_method()`.
See: https://bugs.torproject.org/21662
This patch refactors the `torgzip` module to allow us to extend a common
compression API to support multiple compression backends.
Additionally we move the gzip/zlib code into its own module under the
name `compress_zlib`.
See https://bugs.torproject.org/21664
