I ran our internal integration test suite against the current core+client commits. I didn't find much, just two notes:
1. The async client has started decompressing responses. I had to add a call to `.disableContentCompression()`. This API is new in 5.6. This may be an issue for libraries that use the async client, since it makes it harder to "straddle" multiple versions of the client and obtain consistent behavior from all of them. 2. Our tests for insecure mode SSL (self-signed certs, obsolete TLS versions, etc) started failing. I had to fix this by adding a `HostnameVerificationPolicy.CLIENT` argument to the `DefaultClientTlsStrategy` constructor call, in addition to the custom `HostnameVerifier` I am already supplying. I think this must have been caused by a constructor delegation change in `DefaultClientTlsStrategy`, where the default policy was changed from `CLIENT` to `null` (which later gets turned into `BOTH`).
