Update Release Notes

doc/qbk/09_releases.qbk

@@ -9,6 +9,82 @@
 
 [section Release Notes]
 
+This version fixes a missing executor work guard in all composed operations
+used in the implementatio. Users who are experiencing crashes related to
+asynchronous completion handlers are encouraged to upgrade.
+
+[heading Boost 1.68]
+
+[*New Features]
+
+The include directory `<beast/experimental>` contains features which are not
+part of the stable public interface but are available anyway. They may change
+in future versions.
+
+* ([issue 1108]) New [link beast.ref.boost__beast__flat_stream `flat_stream`] for working around an SSL stream performance limitation
+
+* ([issue 1151], [issue 595]) New [link beast.ref.boost__beast__http__icy_stream `http::icy_stream`] stream filter allows parsing ICY HTTP response handshakes
+
+* New [link beast.ref.boost__beast__ssl_stream `ssl_stream`] for better SSL performance and move constructability
+
+* New
+  [link beast.ref.boost__beast__test__error `test::connect`],
+  [link beast.ref.boost__beast__test__error `test::error`],
+  [link beast.ref.boost__beast__test__error `test::fail_count`], and
+  [link beast.ref.boost__beast__test__error `test::stream`] utilities for writing unit tests.
+
+* New [link beast.ref.boost__beast__http__is_mutable_body_writer `http::is_mutable_body_writer`] metafunction
+
+[*Improvements]
+
+* ([issue 1109]) Use a shared string for example HTTP server doc roots 
+
+* ([issue 1079]) Add [link beast.ref.boost__beast__handler_ptr.has_value `handler_ptr::has_value`]
+
+* Improvements to [link beast.ref.boost__beast__buffers_adapter `buffers_adapter`]
+
+[*Fixes]
+
+* ([issue 1073]) Fix race in advanced server examples
+
+* ([issue 1076]) Use executor_work_guard in composed operations
+
+* ([issue 1079]) Remove spurious assert
+
+* ([issue 1113]) Add `const` and non-`const` overloads for message based HTTP writes
+
+* ([issue 1119]) Fix unused variable warning
+
+* ([issue 1121]) Examples use the root certificate which matches the fingerprint
+
+* ([issue 1141]) Tidy up composed operation doc
+
+* Tidy up websocket stream javadocs
+
+* Fix move-only arguments in [link beast.ref.boost__beast__bind_handler `bind_handler`]
+
+* Fix [link beast.ref.boost__beast__http__parser `http::parser`] constructor javadoc
+
+* Fix [link beast.ref.boost__beast__buffers_adapter `buffers_adapter`] iterator value type
+
+* Fix [link beast.ref.boost__beast__buffers_adapter.max_size `buffers_adapter::max_size`]
+
+* Fix [link beast.ref.boost__beast__buffers_prefix `buffers_prefix`] iterator decrement
+
+* Fix __Fields__, __FieldsWriter__ concept docs
+
+* Fix __BodyReader__ constructor requirements doc
+
+[*Breaking Changes]
+
+* Remove deprecated `serializer::reader_impl`
+
+* Remove deprecated __Body__ `reader` and `writer` ctor signatures
+
+
+
+
+
 [heading Boost 1.67]
 
 This version fixes significant defects in