permessage-deflate is a compile-time feature (API Change):

fix #849

This adds an additional `bool` template parameter to
`websocket::stream`:

* When deflateSupported is `true`, the stream will be capable
  of negotiating the permessage-deflate websocket extension per
  the configured run-time settings.

* When deflateSupported is `false`, the stream will never negotiate
  the permessage-deflate websocket extension. Furthermore, all of the
  code necessary for implementing the permessage-deflate extension
  will be excluded from function instantiations. The resulting emitted
  object code should be smaller.

test/beast/websocket/stream.cpp

@@ -122,6 +122,8 @@ public:
         BOOST_STATIC_ASSERT(! std::is_move_assignable<
             stream<test::stream&>>::value);
 
+        log << "sizeof(websocket::stream_base<true>) == " <<
+            sizeof(websocket::detail::stream_base<true>) << std::endl;
         log << "sizeof(websocket::stream) == " <<
             sizeof(websocket::stream<test::stream&>) << std::endl;