http-client-branch: update public API @since tags

http-client-branch: remove remaining vestiges of MultiSubscriber and minor doc cleanup

http-client-branch: fix race condition and MT-safety in SmokeTest (fix the fix)

http-client-branch: fix race condition and MT-safety in SmokeTest

http-client-branch: added mapping subscriber, miscellaneous bug fixes and change to discard()/replace() subscribers

http-client-branch: 8196848: SplitResponseSSL test failing intermitently (but rarely) with HttpClientImpl shutting down.

http-client-branch: add several private <init> methods

http-client-branch: more remaining impl types to internal

http-client-branch: move LineSubscriberAdapter to internal

http-client-branch: move ResponseSubscribers to internal

http-client-branch: more binding to 0.0.0.0 instead of localhost/127.0.0.1

http-client-branch: move BufferingSubscriber to internal

http-client-branch: remove redundant null check

http-client-branch: HttpHeadersImpl use more efficient entrySet

http-client-branch: use UTF-8 for all convertions to String

http-client-branch: immutable data Flow